We've had Allie for 3 years now (after initially being told she was male and called her Alfie

We think she wants to play more than we get time for, often going out and catching mice/birds in the daytime, very active.
So my girlfriend has been asking for a kitten for her to bond and play with, after resisting initially I think I'm going to surprise her with one around Christmas. As luck would have it someone at work has just had two kittens, well her cat has, and the easy option would be to take one of those.
Firstly, is there a specific gender that we should go for, I've read that some people think Male are more affectionate, though really I think we would have to choose which gender Allie would bond with best. At 3 would she potentially mother a kitten or would she more likely get territorial?
The girl at work would like to give them away after 8 weeks but said she's willing to keep them for 10 if that's better for them, that would take us into December which would be great for me.
Any thoughts or advice would be greatly appreciated, thanks
