My girlfriend has changed for the worse since her mum ped away?

My girlfriend who I loved very much, has changed a lot since her mum ped away. I totally understand that, I was expecting that when the doctors told her she wasn't going to live for very long. I feel really sorry for her, but I think she is intentionally driving her life to hell. Since her mum ped away (4 months ago) she has cheated on me, dropped out of university from studying pharmacy for 2 years, been arrested and changed her personality. She used to be this lovely caring girl, who used to make sandwiches for homeless people in london, and volunteered at so many places. Now, she has stopped all that and she is so spiteful. I can't talk to her. She insults people so harshly even if they did little to do her wrong and I have to end up apologising for her. She gets drunk way too often, and I don't know what to do. I tried talking to her, me and her dad have tried talking to her. I tried talking to her friends about it. I made several appointments to see a counsellor (which I paid for) and she's skipped them. I don't want to let her go, but it's draining me.