Definitely a personality disorder. She sounds narcissistic. One day they promise you the world the next they don't want anything to do with you. It's not something you can change.

They are fueled by insecurity and a constant inability to feel settled. Being inconsiderate and selfish is all they know and really someone in your situation needs empathy and caring. Non NPD people don't change their minds about things from one day to the next.

You have to just accept it. Some people can't be saved and that burdens not on you. She will wake up in months to come and realise she fucked up her chance at happiness.

Stealing all the money was particularly selfish and indicative of narcissistic behaviour.