I came across the idea of River as a sort of female Master yesterday, in fact (there's a list of 56 ways the Master creates River in order to force the Doctor to live a blissful domestic life with him or something?) and I find I really love the idea. I think I agree--on the surface River does have quite a lot in common with Jack, but ultimately all I see is the location we assume she's from and the flirtiness. She's similar to the Master on a much deeper level, in particular the way in which she treats the Doctor--very much as an equal and to some extent a playmate.

I would prefer if she didn't yoda-fy him and lock him in a cage, though.