Is it OK for your girlfriend to hang out with guys?
Of course it is ok! Just because someone is in a relationship, doesn't mean that neither one of you can't have friends of the opposite sex. If you limit her from seeing her male friends, then she is going to feel trapped, and she will break up with you.
Why do I get jealous when my girlfriend goes out?
You feel jealous because you are insecure about yourself. You feel as if that your girlfriend will leave you for other men. You don't feel like you have the necessary confidence to make sure your girlfriend stay faithful to you despite she is. This insecurity that you have can affect your relationship in the long run.
Is flirting online considered cheating?
If you are in a committed relationship with another person, this is definitely cheating. Flirting online is exactly the same as kissing or sleeping around with someone other than your significant other.