awww...she's so cute.
Isn't there a way to keep them from clawing each others eyes out and become acquainted at the same time? Maybe keep the new kitty in another room for a few days, only bringing her out in a carrier so she's safe until established kitty gets accustomed to her? Cattitude? You ever hear of doing this? I don't know, I was always afraid to bring another cat into the house with Jack.
Like I've said before, I've never really had much of a problem bringing a new cat into the house. I've always been very lucky with laid back kitties.
You can do things like rubbing a small blanket/towel on each cat and let them "smell" each other before you introduce them. Also, you can keep the new kitten in a separate room and allow her to come out slowly. I wouldn't leave them alone for a few weeks until you're sure how it's going. If you don't work, I'd let them wander around together after the first day or so and see how it goes. With one being a kitten and the other being fairly young, I'll bet you don't have many problems.
One thing I would do is get another litter box.
I'm so happy you're getting her.