My husband and I are recently married. During the wedding, one of my MIL's friends (aged 50's/60's) behaved badly (of course at her goading - story for a different day). She did everything from trying to pull me to the ground, to getting drunk, yelling profanities at other guests, antagonize other guests, she finally pulled a much younger guest's arm and threw a drink at her - glass included. This guest did all of the antagonizing and other guests insisting at her to stop culminated at this behavior. There was no 2 way street. My family, my husband, my FIL, and of course me, were categorically mortified by her "real housewives" behavior. We received a half apology where the person made a thousand excuses for her behavior and why it was somehow okay for her to cause such a scene at our wedding. After initially defending some of her actions, my MIL has cut ties with this person.
Now the tricky part, what do we do with this person's gift? Do we return it? If we do, do we provide an explanation? Do we send a thank you note? Keep it and say nothing?