Am I overreacting or in for trouble?
What is the situation?
I'm going to confront a friend I don't see as often as I would like about keeping me from seeing my partner.
It is sounds like a tricky situation. You shouldn't just confront them and should talk to them instead. That will lessen the chances that you are in for trouble.
I'm definitely not interested in creating a problem. I'm going to just address the issue and fix it.
That's a very mature way to handle this conflict.  It shows wisdom on your part!