she is going in for a check up Friday. Her shaking concerned me because she shouldn't be cold.I don't have much experience with cats in heat, but 4 months is actually plenty old enough to get spayed, and then she won't have to deal with being in heat any more. Kittens heal from the surgery faster than adults. She does need to be well to have the surgery, though, so it would be good to take her in for a check up first to make sure.