So it's a high school relationship. We have had quite a while but have our fair share of broken unfaithful moments. However that was a while ago, now I am hearing this rumor just from one close friend that a guy showed my friend messages in which my current gf was calling him babe and wanting to kiss him. The close friend that told me about it knows both me and gf so I doubt she would want to say she knows.. However I dont have proof and I do not want to let gf get away with it. I would break up with her :/ but how can i.get proof. Or overall what should I do?