Depends on the degree, IMO. People have lives outside of their relationships, and have friends, both male and female. Its also ok to feel a little jealousy about the person you love. Its almost instinctual.

Trust is quinessential in a relationship though. If you don't feel secure about her actions, maybe you need to talk to her. Don't be accusative, but make it known that you are a little concerned. Its not an easy subject to broach though, so tread carefully. Still, the two of you should be able to talk things out openly and honestly. If you can't, maybe thats a warning flag?