Ask her to send the clothes back even if they are dirty. I know I am a bad DIL but if I do not bag up the clothes my MIL sends DD home in and they get thrown in the pile with all of the other dirty clothes she will never get them back. I do send a change of clothes just for DD to come home in when she spends the night but my MIL likes to put the clothes on her that she has for DD at her house and 75% of the time DD is sleeping in MIL's clothes when DH picks her up.