<human>: Can you give me the gist of the text in a nutshell?

23 M here. My girlfriend of about a year and 6 months has always been quiet/ withdrawn/ antisocial. However, recently she has become incredibly self-deprecating, self-loathing, and is generally getting very pessimistic and negative. Her family is a huge part of the problem, and often tell her she's dumb, or useless, or worthless. And apparently she's decided to take it to heart despite what I say, what her friends say, and what her professors say. I thought at first that she was just stressing out under school pressure, but it has persisted for about 4 months now, and gotten worse. I'm really beginning to feel it's destroying our relationship, because I can't talk to her without having to turn everything I say into a pep speech, and then at the end, she just says "Whatever" and goes to bed. I have no idea how to proceed, I love her to death, but she's vehemently against getting professional help, and I'm not sure how much longer I can put up with 24/7 negativity and shit.
<bot>: GF's family calls her worthless/ useless, and she has bought into it. Now her constant negativity and self-loathing is getting even worse, and starting to affect our relationship.