'I thought my mother-in-law was just difficult. Then I spoke to a psychiatrist.'

Let me start off by saying that I'm fully aware that a large percentage of the world believes their mother-in-law to be pathologically problematic. To the extent that if everyone who uttered the frustrated words "she's a bloody narcissist!" over debriefing cocktails with friends was correct, there'd be nary a single female baby boomer in all the land without a diagnosis. 

Having said that, it's quite likely that my MIL does deserve a diagnosis, a fact which eluded me for much of my marriage. 

I met my husband Todd* young — we were both in our early twenties, and at the time I remember brushing off his wariness around communicating with his mother as the pushback of a young man out on his own for the first time. 

"She can be… difficult," he warned me before we walked into his family home, six months into dating, so I could meet his parents. 

"She just has a lot of opinions."

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Coming from an immigrant family, where strong opinions are as freely offered as second servings of lamb kofta, I wasn't fazed.

The first meeting made me convinced my then-boyfriend was being too hard on his mother. I was presented with a charming, attentive and interesting woman who hosted like Martha Stewart and was the life of the party. She was affectionate, warm, and very interested in me. I felt immediately welcomed into the fold, something that only increased over the coming months, when she invited me back multiple times, once even offering to take me out for dinner without my boyfriend.

The first sign that something was a bit off was when we began discussing Christmas plans. By this stage, we'd been together for about a year, and I'd asked Todd if he wanted to come to Melbourne with me to spend the holiday with my family. We bought plane tickets (we were living in Brisbane at the time) and decided to leave late on Christmas Eve so we could spend the day before celebrating with his family, who have a traditional family BBQ on the 24th each year.

When Todd called his mum to let her know, she lost it. She screamed at him over the phone, then refused to answer his calls or emails for a week-and-a-half. Then, one day, as suddenly as it had began, the storm lifted. She sent him a text as if nothing had happened, asking if we were still on for dinner at the pub that weekend. No one ever talked about the tantrum again.

"She explodes sometimes," explained Todd warily. "It's easier to just let it blow over."

From then on, there were countless more 'explosions' from Todd's mum, but they were interspersed with generosity and fun times as well. Like the rest of his family, I got used to the idea of a certain level of unpredictability. Would we get the fun, let's-do-karaoke-together version of my MIL, or would she sit in the corner getting steadily more drunk, and make thinly-veiled comments about my weight? 

It wasn't until a few years ago, when we hosted a first birthday party for our daughter, that my MIL's behaviour was put into context.

A dear friend of mine, Rachel*, was in attendance. Rachel also happens to be a psychiatrist. Having met Todd's mum at our wedding briefly, and heard my various complaints about her behaviour over the years, this friend was well-versed in our history. 

However, having been tasked with making the cake (yes, this Type A specialist doctor is also an incredible cake decorator) she came over earlier in the day to drop it off. I was out at the shops, so it was my MIL — who'd also offered to come and help set up — who answered the door. 

Apparently incensed that we'd outsourced the cake to a friend and not to her, my mother-in-law launched into a bizarre tirade against my well-meaning friend, much to her shock. 

"She was red in the face and biting back this seething rage," recalls Rachel, "it was a hugely disproportionate response."

When I returned from the shops 30 minutes later, Rachel was gone and there was a flurry of texts on my phone from her. 

"Have you ever considered that your MIL might have Borderline Personality Disorder?" Rachel asked.

Qualifying her opinion with the usual "I could never make an official diagnosis without seeing her several times" preamble, Rachel said that Todd's mother's behaviour before the party — along with the several instances I'd told her about — were consistent with a diagnosis of BPD, specifically the 'petulant' subtype, which was characterised by being explosive when their needs are not met, problems in relationships, passive-aggressive behaviour and emotional instability.

Affecting between two and six per cent of Australians (although somewhat under-diagnosed, according to Rachel), BPD can be tricky — but not impossible — to treat. 

I shared some of the links Rachel sent me with Todd, who looked as though a lightbulb had finally gone off in his head.

"This is mum," he said, wide-eyed, "to a tee."

In spite of Rachel's advice that suggesting to his mother she should see someone for a diagnosis might not go well, Todd tried. It did not go well. When he floated the idea with his brother, however, he said it was something he'd been wondering himself, independently.

A few years on, not much has changed with his mother, apart from the fact that as well as being better with our boundaries, we have a lot more understanding of what might be going on with her.

We're hopeful that some time in the future she might be able to understand that a lot of the problems she has in her personal relationships might be to do with an underlying diagnosis, but in the meantime, we're able to separate her extreme actions from who she is as a person. Mostly. 

*Names have been changed.

Feature Image: Getty.