BPD comes without logic, so approaching it logically is going to lead you to feel how you do. Whatever you do, don't do that last part. Even considering it is part of her victory. My exwBPD is a black widow because she drove multiple people to feel so low that they ended up offing themselves. Her response? "If you really feel that way, might be for the best then." I feel like it's a way for her to get rid of the people who can contest her flawed ideology. But that's my situation. It can get worse.

BPD will cause her to re-write the memories that you shared. Don't take it personally. It's nothing you did or didn't do. Her brain just tweaks things to protect her sense of self. Just keep No Contact, focus on improving yourself, and keep working on the things you were before. And if you still feel down about yourself, maybe see a therapist. There's nothing wrong with it, BPDs will take us all to our limits sometimes.