I'm sorry that you're feeling an extra loss just before having to re-enter a hellish situation growli.
At the same time... I sorta wish your T had done this for you sooner. Your attachment is unhealthy (as you've literally viewed her as a new mom) and she should have realised it sooner and taken action to help you readjust to just viewing as her as "like a mother-figure".
I'm sorry that you have less than a week to make that readjustment.
I think in the long run this might be good for you - because you sorta have no choice now but to learn how to have a healthy relationship/attachment with someone. I just wish that you could have learned this in a more gradual manner alongside learning some self-care.
I understand that it's super-difficult when you don't really even understand the concept. And that 2 months is a very short time - which is exactly why I feel sad that it's taken until the last 5 days for your T to really push you to start learning!
I know that my message is probably going to not come across very well.. but I do mean well. If I knew how to have a healthy attachment to someone I'd gladly try to offer advice... but I tend to keep people are a very far distance and I sort of snowball to nearly-clingy when I do open up (even if I don't really show it as I keep that clinginess inside).
ETA: (you posted while I was typing so didn't see your latest) Your anger is totally justified. And I know that it's hard to learn to love yourself... but you know... I don't love myself either, but I can say with absolute certainty that you can learn to take care of yourself (emotionally and physically and mentally) fairly well even if you don't. I've learned to like myself... sometimes. Through learning how to take care of myself.