MIL trying to be ME!

I honestly don't know what to do. Things have gotten so creepy with my MIL. In the beginning of me and my husband's marriage we didn't see his mom and he never invited her to our wedding. They got back in contact last year and she has hated me since she met me. She's never made an effort to form any type of relationship and she is constantly calling my husband with favors and expecting him to drop everything for her and then throws a temper tantrum when he doesn't. Lately she's started completely copying me. Back in January she died her hair red like mine and then cut her hair like mine. She started dressing like me. We all went out to the lake for memorial Day and she "forgot" her swim suit and went to Walmart to buy a bikini that was the exact same bikini I had. I tested my theory that she was copying me and told her that I was changing my hair color to black and showed her a picture if the hair i was getting. Low and behold she changed her hair to blue and I DIDN'T change my hair. She asked what happened and I said I changed my mind and she got upset asking why I would change my mind and was just overall horrible. This is so weird and creepy and idk what to do.