MOH problems-feelin betrayed!

I need to know if i am overreacting!! My MOH is a bridesmaid in her brothers wedding, who are both my 1st cousins, which is 6 months before mine. I am planning this wedding from CT so i have to be on top of things because i don't want extra stress i don't need down the line..
Ok well we already went dress shopping together for the bridesmaid dresses -picked a first and second choice and we both agreed we would wait till the end of the year to order them. WELL she goes shopping with her future sister in law and picks out 2 dresses that are EXACTLY the same as my choices. the dress they wound up ordering for that wedding is the same style, same cut, complete with a bow in the same spot. I feel backstabbed, i don't like my future cousin-in law, i am very civil to her for the family, and i no way do i want my wedding to resemble hers..My MOH reply-it's 2 different weddings and no one would notice. Well i know!! she even admitted she knew they were the same and she was one of the 2 girls who even picked out the dresses!! Am i overeacting for feeling betrayed? HELP!! I don't feel like i can tell her anything about my wedding until after her brothers so i don't wind up seeing my favors, flowers, gifts showing up at that wedding...

I would be upset too!!!... U r not over reacting... U should demote her to a bm and find someone else to be your moh

I think I would be upset that she didn't consult with you first?? But maybe she feels that getting two different dresses that would each cost a few hundred bucks and alterations too maybe be too much for her budget wise..maybe she figured she can wear the same one for each? Talk to her and see if she would be willing to buy the other dress you two liked for your wedding. What a bummer...
I hope it all works out