Not really a medical problem but there's a health issue here. No you shouldn't trust her. He behavior hasn't been trustworthy. The fact that you resumed a monogamous relationship with someone that dumped you for another man less than 24 hours ago is a serious red-flag about your self-esteem. The fact that she has a close relationship with this guy and other male friends is obviously eroding your sense of stability in the relationship. Tell her it's bothering you and you feel like you can't trust her. If the relationship is important to her she'll talk things out with you. Your relationship should support and help your self esteem grow. If your girlfriend makes you feel insecure or frustrated that relationship isn't healthy for you.

i wouldnt trust her! she broke up with you for another guy. she probably found out that it wasnt what it's crack up to be being with him, so she went back to you.
it sounds like she is playing games.
trust your instincts!!!!!