This sucks bro. Recently went through something like this. She ended up going through with the cheating.

If your finance hasn’t cheated on you yet, it’s time to really sit down and have a talk about your relationship. Why does she feel the need to talk to only this guy about her hobbies? Why can’t she talk to you or her other friends? You gotta find out why she’s exploring elsewhere. If the physical cheating hasn’t happened, the emotional cheating has already started. Was it because your mental illness? Is she willing to work with you while you work on your mental illness so you can be better and be there for her and for your relationship? Relationships are great when everything is sunshine and rainbows. But when shit hits the fan, I.e. when you have a bad depressive episode or anxiety attacks. Will this woman be patient and forgiving and kind enough to not only overlook your shortcoming during your hard time but help you and care for you?

Sometimes it’s best to walk away before the actual cheating happens.