7. She is always out with friends that I don’t know.
“Of course I’m not gonna tell him that I’m out with my male friends. I make it sound vague.” If she is not up-front with you about her circle of friends, she may be up to something. If you notice her behavior is becoming too secretive, ask her to elaborate on her whereabouts and nip it in the bud before it becomes a full-blown affair.