I dont understand this feline leukemia...?

im sorry to hear about your cat . i have had several cats with this disese.

it is not like the lukemia that humans can have. it is more comparable to aids . 1/3 of cats will survive this ( according to my vet so if that is wrong blame him not me.) and they will get very sick once or twice. however if they can bounce back they typically will survive . it ALL depends on if the cat has the strentgh to fight back . in other words keep him hydrated and feed him calorie rich foods . also so vets will give the cat some anti biotics. There isnt different types of feline leuk. just different ways each cat is affected. a good thing to have handy when the cat gets sick is to have an iv so you can be SURE it soesnt hydrate. and never put the cat down because of this disese because just when you think it might not put out it does ive expirenced this several times and it is amazing how resiliant these animals can be ,

Who suggested the bone marrow test? Bone marrow tests are painful. Even though the cat will be anesthetized for the procedure, it will be painful for several days after the test.

Feline Leukemia is incurable. Doing a bone marrow test is to get a diagnosis, not find out how bad a disease is once the animal has one. They are expensive and in my opinion, FOR THIS SITUATION, not warranted. The cat already has the disease, we know it's incurable, what can be gleaned from a bone marrow test? The vet can certainly try interferon, but that has limited success in slowing the progression.

You'd be putting your cat through a painful procedure for very little to no benefit.

The only thing to do now is to make the cat an INDOOR ONLY cat, because she will infect every cat she comes into contact with. Keeping her inside will also keep her healthier for longer.