My MIL is a bit like this, she buys dd clothes because she loves shopping which is fine but then they don't come home, likes to keep a couple of best dresses there so we never see her in them, goodness know what she thinks I'll do with them but they are kept away from our house.
DD does go to stay for a few days during holidays, not because we need them to have her but because we don't live nearby and I know they miss her and love spending time with her. MIL has told me and dd seperatly that I shouldn't have any more children because dd is so special, I didn't say anything cause I was rather shocked by that comment and just stood there with a wtf expression on my face. MIL openly admitts that dd is her favourite gc which I think is a terrible thing to say. She also was very open about the fact that 2 of her 4 children were her favourites, the other 2 now have nothing to do with the family, I have to admit I don't know all of the in an outs of what went on but it must be pretty horrible being awear that your own mother prefers your siblings to you.
I ignore alot of what gets said. Both MIL/FIL say alot of things that I disagree with but i ignore things rather than getting into an argument, got to pick your battles. Even DH says he switches off to some degree when on the phone to them and he is close to his parents.
I think my biggest pet hate is when they give me the "we've brought up 4 children you know, we do know what to do" and yes they have but alot has changed in 40-50 years since they did it and my parenting style is different, guildlines have changed from when I had dd to now 8 years (I'm expecting again) also get this line when trying to explain dd medication needs with them and that she can't use soaps, have bubble baths or use fabric softener in her washing, all of which gets ignored, MIL washes all of her clothes when she goes there that I've packed and everything is packed washed but it all comes back with fabric softener so I have to wash it all again. DH has said something many times but it goes in one ear and out the other it seems. It really irritates me but I have a moan to DH then fume to myself for a day until the cycle starts again.
I understand how your feeling but honestly our MIL's are nothing compared to some of the threads I've read on here.
Sorry seem to of gone on a bit.