How can I assimilate a kitten into my family of two ferrets and a very jealous cat?

I just got a very adorable itty bitty kitten and I already have a cat, my ferrets are fine with her but my older cat just doesn't seem to want to accept her. The baby is living in the bathroom at the moment because of this little problem but it's happened before as well when I was taking care of two stray kittens. My older cat has never had a problem with other older cats (which is weird) but whenever theres a kitten all she wants to do is charge at it and hiss in its face. Please Help! What Can I Do To Make Things Better and More Comfortable For BOTH Cats??