What steps has she taken through out the relationship to be communicative? to set boundaries? To be clear about her needs and wants and what she feels she is missing?

EVEN if she did all that and received an absolute brick wall at every turn- still not "OK" for her to cheat.

If you aren't getting what you want out of a relationship, you work on it. You don't want to work on it, you should still respect the other person and the time you spent together and be honest- inform them you need to move on, if that is the case.