My bridesmaid doesn't care boyfriend birthday is more important than Rehearsal Dinner

So my one bridesmaid who has been one of my best friends for over 10 years, apparently thinks my wedding is a joke. Now I'm not faulting her for this her brother is getting married the month after me so she can't make it to my bachorlette. But last night she texted me asking when the rehearsal dinner is and she said that is going to be a problem, that's her boyfriend's bday, she hasn't even been with this guy for a year. So I'm so sorry my rehearsal dinner has to take a back seat to your boyfriend and if he tells her not to go he is a jerk! She can go out with him the following day, the day before or even the week after. I asked you because you are one of my best friends but apparently my wedding doesn't matter. This is beyond hurtful and rude I don't even know what to say to her.