HELP WITH BMs DRESSES!!!

I ordered my BMs dresses from netbride.com because my BMs didn't want to spend so much money. They give me a hard time with sizes. I was still feeling guilty about ordering dresses one size bigger because I didn't trust hte sizes they told me. Now they get their dresses and one of them is already telling me she's normally a size 8 (mind you she told me she;s a size 6)but there's absolutely no way she'd fit in this size 8!!! All this after I e-mailed them the size charts a million times! I think I'm going to lose my mind! With barely 10 weeks to my wedding...what should I do?