I'd be a bit hesitant to suggest just a single prime lens for her. She's probably used to having a bit of zoom capability from her P&S. You did say that she already has used the 35mm, though, so I might be wrong about that. The cost of the D5000, kit lens and 35mm should be about the same as the D90 and a kit lens. I'd suggest the D5000, with either just the kit, or the kit and the 35mm, unless you think she will get serious about photography, in which case she will probably quickly outgrow the D5000.
EDIT: Jeez 3 new posts in the time it took me to type this. If she says she'll be happy with just the prime, I'm sure that's fine.