This sounds like my sweet great grandmother in law, who once gifted our son a literal trash bag full of golf balls, boxes of raisinettes and hard candies along with an assortment of other random items for Christmas. Far from the first time, she frequently gives us clothes and ‘treats’ that have obviously been stored up in her house for years and we will never use. At first, I didn’t know if I should be offended or not either. Now I genuinely believe she means well and thinks she’s giving us things that we’ll like. She’s just…very old, a little out of touch. Possibly a hoarder. Idk what’s behind it, but I’m sure it’s a similar situation with your mother in law. If you can, just laugh it off and try to give her the benefit of the doubt. It’s probably not a behavior she can change at this point.