I think the more cats you have, the easier it is for new ones to be accepted. At Patsy's today, she had about ten adult cats of differing ages roaming about, very friendly with each other, and all of them eager to get to know us. :-) I think it's like the boarding cattery: they're a lot less territorial together.

I'll just have to hope the kitten gets on with both cats and see how it goes. Otherwise we might have to get another kitten for her; always a possibility, though I'm really hoping it all works out.