Should I change my plans for her birthday, or should she change hers for mine?

My girlfriend wants me to hang out with her on her birthday, but it's karaoke night at my favorite pub. I go there every week with my friends, but she wants me to skip it this week to have dinner and drinks with her friends for her birthday. I told her if she really wanted to see me on her birthday she could come hang out with me and my friends at the pub, but she didn't like that idea. She said I could bring my friends to dinner too, but I just want to sing karaoke like I do every week. Is she being totally unfair for wanting me to change my plans for her when she won't change hers for mine?