I'd question her about the stuff that has been bothering you. You said that when you do question her about things, that she gets upset and doesn't want to talk about it. Well, I think you have to take that chance, to see if you're in a relationship worth saving.
My wife does the same things as your girlfriend, but to a much lesser extent. She chats with friends online, but not all day and night, and she goes out with friends that I have nothing in common with, maybe once every few weeks, so most times I don't go out with them. When I called her out on some things, she cut back on her 'me' time, and I cut back on being an overbearing ass.
If you call her out on the things that have been bothering you, then you'll know if you either made the right choice or the wrong choice. Hope it works out for you.