Just remember that communication and trust are pretty much the two core components that make up a relationship. If one has a lapse, the other needs to pick up the slack.
So if there's been a trust hit, then there needs to be twice as much communication. And pure, honest communication; but that does require both sides. Try putting yourself in her shoes, as someone who maybe has been untrue but also as someone who hasn't done anything wrong.
Maybe she has been talking to someone, but maybe it's because there's something under the surface and you just both need to communicate better. Unless you're involved with a complete sociopath, people will sometimes act out/seek out what they're feeling is missing in their life. But people usually don't actually talk to their partner about it because they're afraid or nervous of their reaction.
I've been in that situation too, then after we've actually brought things into the open, rather than just hoping the other person should just KNOW, all of the sudden things are better..and if there was something going on which was affecting the trust, the person acting out will usually stop since they feel their needs/feelings are being addressed. Of course, if the problems aren't fixed, the pattern will repeat and slowly become toxic.
The best way to approach it is to take the high road, go to her (tomorrow) and ask if she feels there's anything wrong in the relationship, maybe something she'd like from you...it's a waste of energy to focus on who she's talking to, and equally pointless to ever spend a second of time on it..people will do what they want to do, regardless if someone is watching, they'll just be more careful in the future to not get caught. Gotta focus on the root of the issues, open, honest, communication. It's both the EASIEST and HARDEST thing to do.
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