I think its superb she was allowed to join the team. If she can hang with the physical beating involved with contact sports (and the position she's playing) I see absolutely no problem with her getting out there.
When a female can perform the same duties as a male (in whatever the context may be), theres pretty much no reason to have a gender barrier placed up to bar her from whatever that task is.
---------- Post added 2012-09-15 at 05:28 PM ----------
I'm pretty sure she knows the risk she is taking though. What teenage competitive male wouldn't want to shut down the femal QB who just juked him and made the pass? Guys are going to have a grudge against her, due to the gender stereotype. Thats a given. I'm sure her coach at the very least is keeping an eye out for the heavy hitting opposing players, and giving her pointers "hey, see number 42? You need to shake him hardcore, or he's gonna flatten you"
Females have a higher tolerance to pain, are more flexible, and have the potential to have better hand eye coordination than males (however, the concentration factor involved is yet to be determined... see 40+ years of female driver jokes for examples)