Just smile and say thank you - wear them once or twice, and then send them on their way to Oxfam or Goodwill.
My MIL thinks it's cute to buy the same suit (sometimes even in the same color) for all the bahus when I am visiting Pak. Keep in mind that there is a 14 year age difference between the eldest and me, so you can just imagine what kind of idiocy that is. Apart from that, I receive either nothing or hand-me-downs, so you should feel fortunate that your MIL seems to care about you, she just has bad taste.