As a polyamorous person I would like to say, you don't get to make up your own mind. You and the other person/people you are involved with get to decide what the boundaries of the relationship are. If you don't like your partner's boundaries, then the two of you either need to work that through or start seeing other people.

I really don't understand writing a story where you justify how oral sex isn't cheating, but then say that you don't like the thought of your girlfriend having a celebrity crush.