'Kelly Osbourne, a mistress didn't ruin your family, you did.'

Kelly Osbourne has tweeted the phone number of Michelle Pugh – her dad’s alleged mistress, and the woman she blames for ruining her parent’s marriage – to the world.

Yes, that's Kelly Osbourne. Who has 4.07 MILLION followers on twitter. Who makes headlines every other week. Who already had the world sending her mother, and her family, messages of support in what must be a difficult time.

It was never going to be a small-time tweet, it was going to reach tens-of-millions, spread like wild fire, and make Pugh's life an absolute living hell. That's why she did it.

Her justification?

"Don't fuck with my family, don't fuck with my momma, and don't fuck with me."

Fair call (although we all know there's one person in that family where that boat has sailed).

As a child of divorced parents, I can't tell you the things I've thought about doing to the person who 'home-wrecked' my parents' marriage. I wanted to go to their house, call their children, pee in their shampoo bottle, slash the tyres to their stupid, I-don't-want-you-anywhere-near-my-life car.

But I didn't. Because there is a line.

Kelly is 31 and she crossed it. (The habit must run in the family)

All those thoughts of revenge. All that anger, hurt and fear. The jealousy that a person who should mean nothing is providing one of your parent's with something that you, or your family, cannot give them. All those don't-fuck-with-me's? Those feelings are justified, and can be felt by anyone in the same position - no matter their age, background, or type of family.

What isn't justified is that Kelly acted on them in front of a global audience (many of whom are fans and will no doubt come keyboarding out to her defence). Kind of like a toddler full of rage. Because that isn't brave, or bass-ass or funny, as perhaps she intended it to be.  Kelly consciously used her position of power to target and hurt a woman who is in no position to defend herself against the absolute force field that is Kelly Osbourne - and the force field that is her fans. It's the digital equivalent of a school gang corridor cornering, multiplied by millions.

What? Do the Osbourne's just go around having "alleged" affairs and calling to arms their fans and it's all okay and whatever happens is not their fault, because they are, well, Osbournes?

What also isn't justified is absolving her father of any responsibility. Ozzie was the married one in the bed. Ozzie is not an ostrich who can't think for himself. This married man made a choice to cheat. And Kelly is letting him get away with it.

Kelly is an adult herself. While this doesn't necessarily make dealing with a ruined family any easier, it should at least give her enough insight to know that no one is perfect. And that her dad is just as much to blame for this affair as the giver of "blowjobs" (did we not learn anything from Monica Lewinsky?).

But Kelly doesn't realise this. She is showing this in the embarrassing (yes, it's embarrassing) and narrow-minded way she is responding to comments on the phone-number tweet.

For example:

(Not sure how Susan Sarandon, Hillary Clinton, Bernie Sanders or Gloria Steinem - who are all approaching or have surpassed 70 - would feel about the implication that they have no control over the person they're sharing their bed with.)

Kelly's actions are disappointing because she does have a voice. And she could have used for something more than school-yard-style garbage. Why couldn't Kelly use her power and influence to make a statement that didn't reduce her otherwise-powerful, and often-pro-feminist-pro-empowering image, to the of level of Mean Girls' Regina George?

Maybe it wouldn't have made as as many headlines. All of a sudden, Kelly's name is the headline in this drama that is enveloping their family. Calculated? Possibly, but I certainly hope not. Deliberately enabling a world of fans to hate and abuse a single woman is bad enough in itself. Doing this to raise your own profile, is something else entirely.

By all means, Kelly, feel what you feel. Pugh is not innocent, and you can hate her, and you can live with an undying urge to slash her tyres, but do this in private, with your friends and your family. Do this in a way that is smart, not embarrassing. In a way that you still maintain your integrity and this - more than anything else - will show the world the power of you and your family.

Because drawing that line shows more strength than the path you have taken. And I think your family may need someone to show some strength right now.

Watch next: Sharon Osbourne opens up on Ozzy cheating with two nannies.