i couldn't say no and did a couple of things but when they started to bring over their DH pants and ect I just took for over 6 months before they got it back with each time they asked about it I told them I just didn't have time.(When I did finally give them back he had out grown them LOL and I was never asked again.
So what would happen if you just took a long time in getting it back to her instead of being so prompt?? maybe she will figure out you have more things that you do besides being at her beck and call?