Give Misty a few more days to adjust to the kitten and then make a decision. Introducing a new kitten to a household with two established cats is always problematic, especially when one of the established cats is a female...They tend to be much more territorial than males in general. I'd suggest closing the kitten in a bedroom with her supplies when you're not there and only allowing supervised visits for awhile.
When we introduced a new kitten to a 7 year old female, the sparks few for about 2 weeks. By sparks I mean hissing, spitting, clawing, biting, the whole nine yards. After that two weeks though, the tensions began to lessen as the older cat came to understand that this youngster wasn't leaving.
I won't say that they are buddy-buddy now. They still have minor fights (fur gets pulled at the worst) and they won't be caught dead on the same couch together, but I would definitely call the situation livable.
So, I would say, give your kitties at least two weeks. If things are still this hostile, you might want to consider finding another home for the kitten.