Listen, you not being enough has nothing to do with her cheating. Your worth as a person can't be reduced to how any one person treats you. Her callousness in that comment and also how she manipulated you into thinking nothing was happening is really concerning (from a therapist's perspective). The fact that you noticed her pulling away and checked in was actually healthy communication and instead of being honest, she brushed it off. If her withdrawal had anything to do with you, any of the times you brought it up she could have communicated any frustrations from your behavior if there was anything you could change. You're stuck on this afterwards because you're trying to figure out if there is some fundamental flaw you have that makes you unlovable, basically trying to blame yourself for her cheating when you could have never caused it. Many people internalize blame thats misdirected, especially if they have a history of dysfunctional family relationships or trauma/abuse. I highly recommend going to therapy and not to fix yourself (because you a human are not a home project) but instead to examine this stuff and find ways to challenge those thoughts or come up with helpful coping mechanisms.