Hello Dorcas
We've had this conversation before 
Always nice to know I'm not alone.
I think the catharsis is an important part here, and I haven't found a way of defusing her, except to let her go through whatever it is she's going to go through to get to the point she can have a cathartic sob and cuddle. So I try to speed it along too sometimes. If I do anything else, if I try and calm her, I think I've managed and ten minutes later she's back to hurling abuse.
I also think it's (often) a choice. I can see her deciding. She'll stand in front of me deciding which way to take whatever is the non-incident that's the trigger.
If it was different circumstances I'd be quite proud of her debating skills - she can take anything you've said in the last week and use it as an accusation.
And the rest of the time she's an absolute delight. 😐
But she certainly knows how to push my buttons, and too often they're too easily pressed. 
What I'm trying this week is to be more proactive about giving cuddles. I'm always around and not doing anything else in the after school to bedtime bit of the day and when she was younger she used to sit on me for most of that. She's stopped doing that as much, I think distracted by homework and tablet and so on, so I'm trying to make sure that happens even if it's not initiated by her.
(And yes, those that have asked, we're getting seeking help.)