A few things:
The most important thing is "which does she like best?" For me, it's the one that's easiest to use and easiest to carry.
Weight/size. Mike Johnson has had a couple of posts on this recently and it's not to be underestimated. I'm on the big/strong side of female at 6' and found my EOS 1, E1 and 30D a complete PITA to lug around. I sometimes borrow a friend's 350D but with the kit zoom (which is crap) it can be bulky. She's a lot smaller than me and now rarely uses it, preferring her Fuji F20.
With this in mind, what will it be used for? Certainly there is a cache to using a DSLR esp as a teenager - but only if she is using it rather than leaving it at home because it's a PITA to lug about. If she doesn't need the fast shutter response of an SLR because she's concentrating on landscape or architecture, would she be better with a G10 or something?
The Olympus has a 25mm (50mm) pancake lens. This makes it nice and small and might make your job as her instructor easier? I'm terribly curmudgeonly for someone of 26 but I think that primes are by far the best thing to learn with. I also cannot make 50mm work for me consistently (except on APS-C when it becomes a great portrait lens).
Finally - carrying it. No teenage girl is going to be seen dead with a camera bag day to day - and I'm not either. Given that her folks are going to indoctrinate her as to how delicate and precious the camera is, she's not going to use it if she's expected to carry it around in one of those hideous square store freebies. Besides, there is no space for make-up, purse etc in them. The solution is either
http://www.speedgraphic.co.uk/prod.asp?i=1...ndard+SLR+Cover or
http://www.speedgraphic.co.uk/prod.asp?i=1...=Novoflex+Wrap+ thrown in a large handbag.