I just found out my girlfriend is cheating on me with another girl and I'm devastated.
I am so sorry to hear that, that was not very kind of her at all.
Yes, she doesn't like my family and close friends. She says they're from lower social classes and shouldn't be hanging around me.
If anything, I would say that her cheating on you is a blessing in disguise. She gave you a great reason to leave her now that she's proven that she's unfaithful. On top of that she told you to stop seeing your friends which means she's really controlling and you need to get out as soon as you can.
She is right and I'm a bad guy because I don't like them.
Break up with her, and move on with your life, you will be happier in the long run I am sure.