ahh....Fido's bone staining the carpet...something I am all to familiar with. Santa must of gave it to him!
I have almost white carpet and boy do the dogs make a mess on it with their feet and everything. I use resolve carpet cleaner in my cleaner, but for spots like that I spray "Woolite Oxy Deep" on it, let it sit a few minutes and scrub with a wet rag first. That alone will take the spot out. It comes in a blue spray bottle, works great. Be sure she test the cleaner first in an inconspicious spot and don't leave it on too long as you will have "very clean white" spot there. It has even removed dried blood from my white carpet from when my lab had surgery...there was a lot of blood too, not just a little spot. It was a spot about the size of a grapefruit, very dark red. He had laid on his incision and it drained. I didn't think it would ever come out, but it did! I can buy it even in my little local grocery store so she shouldn't have any problem finding it.