My mom made me maid of honor for her wedding&my bros gf is 1 of the bridesmaids & we dont talk??

Just keep your head up, smile, be cool and try to make your Mom's wedding a memorable day. If anyone else acts up, they're going to look bad, not you. Its a special day for your Mom, give her the gift. You can't pick your family, be pleasant, be polite, do the right things even if you don't feel like it.