"She's in there." What no one tells you about raising a child with a disability.

When Samantha Wheeler gave birth to her daughter Charlotte at just 27 weeks, she couldn’t shake the feeling that something was wrong.

“She’ll be fine,” the doctors assured her. Charlotte was tiny, but doctors could “work magic” with premature babies, Samantha was told. There was nothing to worry about.

But Charlotte was Samantha’s second baby, and when she didn’t start to crawl, or talk, Samantha knew it wasn’t normal.

After seeing several doctors, the family were told Charlotte probably had autism. They were encouraged to do their best to care for her, and were given a very vague prognosis. She might speak, they said, but she also might not. Over the next several years, Samantha went from specialist to specialist, trying everything she could to help her daughter learn to communicate. No matter what they tried, however, Charlotte only got worse.

It was when Charlotte was ten or 11 that it became very clear that an autism diagnosis didn’t make sense – suddenly, she started to lose the ability to walk.

“Kids with autism, they can walk,” Samantha tells Mamamia. “So it was really only when she was 14, so much later, that we finally got the diagnosis that she had Rett syndrome.”

Rett syndrome is a genetic disorder that almost exclusively affects females. According to the Brain Foundation, most girls with Rett syndrome develop normally until about six to 18 months of age, when they stop acquiring new skills and may regress from the milestones they’ve already reached, such as crawling and speaking. About 1 in 10,000 girls are diagnosed with Rett syndrome.

The trajectory of Rett syndrome starts with delays in motor skills, before a rapid destruction of hand skills and spoken language abilities between the ages of one and four. Characteristic movements like repeated hand clapping and hand wringing often arise at this time, as well as a withdrawal from social interaction, with some of these behaviours looking much like autism.

Between two and ten, these symptoms tend to stabilise, before another stage of motor deterioration. Like Charlotte, some girls who have learned to walk lose this ability, and they experience increased muscle weakness, sustained muscle contractions, and rapid, jerky movements.

For Samantha, the diagnosis was like "this massive elephant off my shoulders". For years, she had "felt like I was doing everything, and my daughter screams and hits and doesn't seem to like me".

"So to finally get that diagnosis at 14 was huge," she says.

Samantha describes Charlotte's symptoms with the level of detail of a person who has spent years and years studying them. Charlotte's dyspraxia meant she could only say one-off words, like 'mum' or 'wee wee'. "But that didn't always mean 'wee wee'," Samantha says. "Sometimes it meant take me away from here, I don't want to be doing this."

Charlotte also displayed hand wringing - with her hands pressed so tightly together she couldn't release them. This meant she couldn't feed herself, or use communication aids that require hand movements.

"She's small for her age, so she looks like she's about ten now even though she's 21," Samantha says. "And she has very small feet, very small, little sweaty feet."

But the cardinal feature Samantha has seen in countless girls with Rett syndrome is the alertness in their eyes. "The rest of them looks a little saggy, and dribbly, but their eyes shine," she explains. "You can see it in all the girls that I've met, where they're in there, and there's light in their eyes."

This awareness is perhaps what makes Charlotte's condition so frustrating. In kindergarten, Samantha describes her daughter being "intellectually able" but "non-verbal," meaning the only way for her to express herself was through biting people or pulling other kid's hair. It was a mainstream school, and Charlotte "was so aggressive we got told to leave," Samantha says. For the next few years Charlotte went to a school for children with autism, but "she sort of never really fitted in there". When she was seven, she went to a special school in Brisbane, with kids with all different disabilities.

Charlotte, her mum says, can tell when she's being treated differently. Samantha remembers enrolling her in a 'normal' ballet class in their local area, and "the ladies were so lovely and they let Charlotte come and she loved it, absolutely loved it". But the following year, the ballet school organised a special needs class, and invited Charlotte to join in.

"She didn't want a bar of it," Samantha says.

"She didn't want to go with that class, she wanted to go with her friends who were doing proper ballet. And yes, she couldn't do proper ballet, but she felt like she was doing proper ballet, but when it was a special needs class, they didn't put their hair in buns, they didn't put ballet music on, and that's not what she wanted to do."

Even now, Charlotte is particularly sensitive to people who speak to her "like she's stupid". They talk loudly, and close to her face, and she knows she's being treated in a different way to everyone else.

"I say to people, please, by all means, come and say hello, but keep the same rules in play that you have when interacting with another normal person," Samantha tells Mamamia. "You know, talk in a normal voice, give eye contact, and keep a normal body language distance apart. Because when people press their face up close and they talk like she's deaf, she spits, she's like 'back off'. Then I'm embarrassed, and the person goes away, and it's all a disaster."

Speaking to Samantha, it's clear that Charlotte's disability affects everyone who loves her. Charlotte's older sister, Beth, who is now 23, had to grow up being "the quiet, good girl, who didn't complain, didn't ask for anything".

"I think the way it impacted her was that not only was she a bit embarrassed to be seen out in public with her sister, but she also grew up quickly," Samantha says of Beth. "It meant that making friends was hard, and finding her tribe if you like. No one was like her."

The other obstacle Samantha observed between her daughters was how hard it is "to love someone who doesn't look like they're loving you back".

"Back when [they were growing up], she'd pinch Beth's skin or pull her hair or bite her so that's hard to interpret as love. So when you're only young, say Beth was 12, it was very hard for her to think that her sister even loved her."

But now 21, Charlotte has found her own ways to love the people in her life.

"Her eyes are the only part of her body not affected by this horrible mutation," Samantha says. "You can tell that she is looking at you with love now."

"The little moments are, well, you might be sitting on the couch with her, she loves David Attenborough, so you put David Attenborough on, and you're catching up on emails while you're sitting there with her, and you look over and see she's not watching the show, she's watching you. And she will break into the most beautiful smile because she's caught your eye, and you've caught her eye, and that just says everything that a word wouldn't say."

Now that she's an adult, Charlotte has settled into her own skin. She's less frustrated and angry, and she has a "lovely sense of humour". All Samantha wants for her daughter - the one she didn't dream of, but who gives her all kinds of gifts she wasn't expecting - is a "fulfilled life". She doesn't want her to be isolated or alone, and she hopes she feels included and loved.

Samantha Wheeler has just published a novel, Everything I've Never Said, about an 11-year-old girl named Ava who has Rett syndrome. It's told from Ava's perspective, and based loosely on Samantha's own experiences raising Charlotte.

In the book, Ava's father comforts his wife with a poem called 'Welcome to Holland'. It uses the metaphor of a person's excitement for a trip to Italy, that immediately turns to disappointment when they land in Holland. Here's an excerpt from the original poem:

"Holland?!?" you say. "What do you mean Holland?? I signed up for Italy! I'm supposed to be in Italy. All my life I've dreamed of going to Italy.

But there’s been a change in the flight plan. They’ve landed in Holland and there you must stay.

The important thing is that they haven’t taken you to a horrible, disgusting, filthy place, full of pestilence, famine and disease. It’s just a different place.

So you must go out and buy new guide books. And you must learn a whole new language. And you will meet a whole new group of people you would never have met.

It’s just a different place.

The end of the piece reads: "If you spend your life mourning the fact that you didn't get to Italy, you may never be free to enjoy the very special, the very lovely things... about Holland."

In the acknowledgements section of her novel - one that tells a moving and nuanced story about disability - Samantha thanks her daughter, Charlotte.

"For giving me an unexpected trip to 'Holland'," she writes, "and teaching me what life's really about."

You can buy Samantha Wheeler's novel Everything I've Never Said here, or visit her website here.