I'm going to break up with my gf over her sketchy actions and drug use
Are you sure that this is what you want to do?
Yes, I really don't like her sketchy acts.
I understand, and I think if she's using drugs and acting in an inappropriate manner, then breaking up with her could be a good idea. It's fine to not want to associate yourself with someone isn't acting appropriately.
She should have chosen better people to hang out with. Who knows if I might get hurt if we get closer.
That's completely reasonable. If her friends are also doing harmful things, then she's going to have a tough time stopping. I don't think it's out of line for you to not want to get closer to her.