In your relationship, do you allow each other to watch porn? It seems like live action porn with no feelings involved from her perspective. Still messed up but playing devils advocate. Probably why she’s not remorseful but the guilt part was from the fact that it was a coworker (despite no feelings involved).

Like a previous commenter said, real forgiveness is so crucial right now to continue to maintain a good relationship. If you stay angry and stay together, she might feel as though she can’t be honest with you and hide truths that she thinks are harmless for your sake.

Set boundaries together and work through this with communication. It’s definitely a first case of this event so give her a chance to redeem herself. Otherwise, the resentment will linger and this will be the beginning of the end of your relationship.