I'm not a fan of the crossbow either, but like was stated before here in NY it is only allowed during gun season and an additional safety course might be needed. If one is not needed, they should be!
About the worst thing you could do is make her try too hard, if she pulls a shoulder muscle, it's crossbow for sure! Like you said," strengthen"!!! Lots of protien, be sure to get enough sleep, arm circles and squat-thrusts! Best of luck and when is your season opener?