maybe she can't lift anything, but she CAN get certified to operate the forklift. c'mon. Even when i worked for a smoothie company I had to lift, fill, deliver, and haul boxes of over 50lbs. I grew a nice set of biceps for it too.
It helped me get into shape, but yes, it does take a toll on the back if you haven't been to an ergonomics class, which they HAVE to send you do if you do heavy lifting.
I'm a manager where I work. Why? Because I have experience as a manager, I have worked in the same industry they are in with RESULTS from my last employ, and I just all out know my shit when it comes to coffee, smoothies, and customer service. Some people just aren't management material. (not to say that your girl isn't... but that other women who say 'yea, they were mean to us' for sake of the argument may just be peons.)
If they never offered her a position just because she's female, well, dunno what you'll get from it. But if she could handle the position and the requirements they ask for... as well as the responsibility... then, sure, it's unfair to HER personally, not ALL women who work there.