If she has been depressed then yes she may look outside the relationship. This is a sign to me that ANY bad time in the relationship she will look outside the relationship. It is completely not taking responsibility when saying "oh, it's my bipolar" because even if bipolar was the catalyst it still holds true that other things were/are going on. I would honestly get therapy for yourself to see if you can move past this. If she wants to work on the relationship I suggest Intensive Out patient treatment before stepping down to Out regular patient. Find out why she continuously comes off her medication. Medication isn't for everyone or there maybe side effects are to intolerable and she needs a psychiatrist that listens.