I am so sorry that you are going through this. I go to yoga at a studio that has a "young,blonde and bendy" clique, so I get it. Fortunately, they rarely get out of bed on weekends for a 7:30 class. It is just the AARP crowd!

Do you love the class? The silly women aside, do you love it? If you do, then don't give up something you love because women can be beechy. Switch classes, confront the other woman, talk to the owner, do whatever you have to do to stay if you love it.