Go big or go home, Canon AE-1 and some lenses on E-bay. You can stay under budget and she can learn more about camera use and maintance than a P&S could ever teach her. It is by all means a disposable SLR, that she can learn on. She could make mistakes and damage something and and learn from it with out putting you out two or three hundred bucks. Then when the time comes she will be better able to acclimate to a dSLR having experience with an SLR, she'll already know how to take care of it and use the basic functions like aperture, different focal lengths and so on.
I humbly disagree with this suggestion. I think film is a mistake in this age group. Firstly, unless you are independantly wealthy,film is an expensive habit to maintain even if the initial investment was low (especially if, as my kids do, she photographs everything in sight). Secondly, at this age group, instant gratification is important (trust me -- I have twin 13 year olds). Digital allows them to see what they did immediately and improves the learning curve incredibly. I think, in the current era, film is not for beginners but for those of us who have experience with it to begin with from 'the olden days', or for those who start with digital and want a new venue for their talents.