I started out on a women's specific Specialized Hardrock. The women's specific worked for me because I'm very small (4"11) and the geometry fit better.
Having the hardtail was great for all around. I used it for paved trails around the city and riding around some beginner single track and fire roads. I've since upgraded to a FSR (but regret selling that bike, would've been nice to have for those "easier" trails with friends)
My best advice would be for her to try riding different models of bikes so she can decide what works best for her. Explain the difference to her about the components (i.e. disc brakes, V-brakes) then ride them to actually feel the difference. When her eyes start to glaze over you've explained too much
I hated mountain biking before this bike, previous bikes I rode were heavy, cheaper bikes and getting a bike that was comfortable meant all the difference.
I think as a beginner I wanted to have a more upright position because it didn't feel like you were going to go over the handle bars. But once I learned the basics of bike positioning (neutral position) I wanted to have a shorter closer cockpit.
We just had friends buy the newer replacement of the WSD Hardrock ( the Myka ?) and she loves it. Price was about $800 CAD.
Good luck! Happy riding!