Advice on a build?

Hello I am building up a hard tail for my daughter who is 15 1/2(always reminds me of the 1/2!) and looking for a little advice/opinions on it.
A little backround she is 5'6 with very long legs and regular torso. She recently joined her high school mt bike team and she was riding a older 17" Specialized Rockhopper (mens frame) with 26" wheels. I didn't want to go out and get her a new bike before knowing whether she was going to like it and the rock hopper was not that bad of a bike( upgraded it to XTR,hydraulic brakes and XTR tubeless wheels).
Well the season ended last month and she liked it so much she deciding to give up her softball career ;) and stick to MTB.
I took her to a few LBS's in the area and try bikes out. I know thats not the best way but I had to find out what she liked.
The problem is because of her long legs, women's specific bikes didn't work for her very well so she tried the mens.
well I ended getting a 2012 17.5" Specialized Stumpjumper 29 frame that I am looking to build up.
I'm looking for some feedback on crank arm length and stem length?
It's hard to go based on her current bike since its a 26er and kinda hard to try to get measurements at the LBS.
Can anyone who is 5'6 with longer legs that might ride a Stumpjumper help out with what crank arm and stem lengths they are currently using?

On my mountain bikes, I like longer crankarms than on my road bikes, so I use 175s on my mountain bikes. I ride with more of a masher style on my mountain bike (by necessity), so the extra leverage is good. For reference, I'm 5'4" with long legs (never measured, but all of my pants are at least 32" long) and I ride a small Niner Jet9 and a small Salsa El Mariachi. Like your daughter, women's specific rarely works for me because of my long arms and legs, and I end up feeling too cramped.

As for stem, have you talked to your shop? They might have some cheap loaners that you could use to dial in fit before spending money on something good.