You already received a lot of good advice. Let me add two comments:
* The size/bulk of the camera
The D90 is particularly big among all the dSLRs. In contrast, the Pentax dSLRs are smaller than average. The K-x is the smallest and the K-7 is just slightly larger.
If you friend has some small hands, the K-x or K-7 should be preferred. Personnally, I have medium sized hands and I prefer the grip of the K-7 over the K-x.
* Weigtht of the camera
A big difference between a P&S and a dSLR is the larger weight of the dSLRs:
- the D90 body weights 703 g (with battery)
- the K-7 body weights 670 g
- the K-x body weigth 515 g
Based upon weight, the K-x is the winner.
Ideally, in a better world, your friend should try the camera herself. However both the D90, K-7 and K-x are great cameras.
If the camera was for my wife, I would choose the K-x because it is very simple; the dial mode is close to a P&S; the K-x weight and size is also more friendly to a woman, in my opinion; and the colours are cute.
NB: I went myself through a similar choice for myself. I chose the K-7 ahead of the K-x and D90.