Friends have made plans on my birthday

Somebody in my group of friends has organised this movie marathon at their place. The issue is it’s on my birthday so I voiced on the group chat today that that day is my birthday and nobody acknowledged it. They just continued saying that they were down to do it that day and that they’ll book work off for it. I wasn’t even expecting them to offer to do another day but they could’ve offered to go out afterwards as it finishes at 9pm. I messaged my girlfriend after (who was also invited) that I guess I’m gonna have to compromise my birthday plans and idk, she just kinda shrugged it off saying that the movie marathon sounds fun and I should just do that on my birthday. This has bugged me as I don’t really wanna do a movie marathon at someone else’s place on my birthday…