BPDFamily.com

Well my ex hated the word LOL, now she uses it
She hated coffee, now she loves it and cant live without it
She hates touching strangers, now she cant get enough of it
She hates clubbing, now she does it every weekend
She doesn't do drugs, now shes a junkie
She posts cringey stuff, that she couldnt stand
She's becoming a mainstream person now, which was her biggest fear

So basically it doesnt matter what they tell you about themselves, they can just change in an instant?
I remember telling her my biggest fear was being cheated on, and thats what she did to me after 6 years of being together
I had to find out all for myself, cause she lied, lied and lied and blamed me for everything.
Made it all seem like my fault that shes breaking up with me.
How can anyone be like this?

They don't be. They are victims of the disorder, but don't know it. The personality just breaks down. Mirroring destructive behavior patterns, role confusion, the unwillingness to accept their own faults, are among the many coping mechanisms of a personality breakdown. This can also happen in organic brain diseases such as dementia and schizophrenia, and show up later on since her mother is mentally ill, and most likely others in her family were as well. Red flags were presented to you, but most of us ignored them. Knowledge is power when we are struggling with incurable diseases. Especially diseases of the brain or an entire personality. You will come to realize one day that this personality disorder will never change, but it wears many masks. If she returns to you as many do, make her get a brain scan. This may help you to see what may have caused her suddenly extreme behavior changes. Also, she may have trauma bonded with someone during the breakdown who has these destructive behaviors as well.    

see the thing is they haven't changed at all.