If it were my mother spending a bunch of money on a camera I wasn't going to use, I'd make sure she knew I appreciated it, and then let her know in advance it's not as "usable" as what I collect and I'd be swapping it for something less collectible and more compatible with my uses. In the future, she can buy some photo film or a book I have on my amazon wish list.
I have also had people gift me cameras when they were moving / cleaning out / to save them from a lawn sale or trash pile. I've generally taken them, knowing fully I wasn't going to use them. I had great success using those as bartering material for cameras I do want.
A neighbor did give me a yashica TLR once. I tried it, put it away for a while, got it out a couple years ago, and have made tons of great photos with it.