AITAH for prioritizing me and my gfs 11 month anniversary over Karaoke Night with the boys?

My friends organized a karaoke night for a few weekends from now, we usually meet up every Friday, but occasionally there’s larger events (like this) that people are extra encouraged to prioritize over the Fridays. However, the date coincides with the 11-month anniversary with the girlfriend. Something special has been planned for weeks, and it's a really important milestone. When the friends were told attendance at karaoke wasn't possible, they became upset. They said they were being ditched for the girlfriend and that she was being prioritized over the friendship. They think an 11-month anniversary isn't that big of a deal and that karaoke should be attended.