If she needs to wait until the last minute and is already stressed about the $$ definitely tell her that it's probably best she's not in it. I had a similar situation, my MOH always talked about being my MOH (friends since middle school) so I asked her and she agreed knowing it was going to be in Mexico. Then came her complaints about how expensive it was and I told her she didn't have to come, we didn't want anyone to stretch their budget too much to come to our wedding. But she made arrangements and said she's in.
I had to schedule our dress fitting around her schedule for her and my sisters. Then came the bachelorette party discussions and she was being difficult with the scheduling and costs. She also asked if I had a backup plan in case the violence was too bad in Cancun at the time of the wedding....major Debbie Downer. In the end she's going to the wedding but not as my MOH and unfortunately it created a lot of unnecessary stress and issues with my mom and my sisters.
If you think she'll end up like this my advice is to cut her out of the wedding now and if she comes to the wedding great, if not don't sweat it. Focus on everyone else that's excited about going and how much fun you're going to have!!
