How does he know she'd take a 50-52 cm bike? I'm just half an inch shorter than her and ride a 44 or 46 cm....I am sure she's got a long ways to grow, but still, 52 cm?! I wouldn't even be able to stand over that one. And if she's "all legs", then she's probably got a short torso so WSD would be even more important. Even though she's a child, I'd suggest to your friend to get her to an LBS for a fitting and not buy her bike over the internet unless he's really sure it will fit properly, based on said fitting.
Good luck!
Emily
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow