1) Cut as much of the flesh off as you can and cook it in water at a very low temperature. A crock pot is really the perfect thing for anything you can fit in it, because you can leave it cooking for a long time. So if you can get a crock pot that's big enough, that'd be perfect. You can use a regular pot on the stovetop, but you can't leave that on all the time. This method doesn't smell too good, so your mom might not be up for it.
2) Drop it in a bucket of water and leave it outside. Pour off the putrescent water once a week or so and refresh. Repeat until clean. This is super gross and smelly, but at least you can keep it outside. After everything has rotted off, you'll still want to try to cook the grease out of it. If you get to this stage, I can ask my wife what the best thing to use for that is. I believe it involves cooking again, but then it's not so smelly. There are a couple of different methods I think for de-greasing stuff.
3) Buy some dermestids You can keep the larvae of these carrion beetles contained in a rubbermaid/aquairum/whatever at an appropriate temperature and they are the best cleaners around. You can order them various places. When you don't have flesh for them to eat, you can give them other things, I think, like dog food.
4) You can start your own dermestid colony by picking some larvae off a carcass you find outside. Everyone has their own native species of dermestids. But really, buying them seems worth it to me.
p.s. I do not recommend burying. It's supposed to work, especially, if you wrap in window screen to contain all the bones in one package, but the timing is tricky. I tried it with a rabbit relatively recently and it was disintegrated when I dug it back up. Left it "in the oven" too long. I should have used the bucket method but I didn't feel like dealing with it.
Also, bleach will damage the bone, so I wouldn't use that. But I believe Kristi has been using acetone with some success for whitening, so once you get it clean and are ready, I can ask about that, too.