With that price bracket her best bet will be used. The nice thing about buying a road bike is that the fit isn't nearly as finicky as with a tri bike. She'll be looking at something in the 48 range, or an XS if they do t-shirt sizing. Given that she's new to riding the key to her being comfortable will be the saddle, reach, and then the roads where you take her out.
Flat pedals with (loose) toe clips may actually be a good starting point as she may be nervous about having her feet "stuck" to the pedals.
Any road bike in her size with 105 or thereabouts components will do her well as long as it hasn't been ridden to death. Then the key will be getting her comfortable not sitting bolt upright as she may remember from riding as a child, and on the road.
<If you're gonna be dumb, you gotta be tough> Get Fitter!
Proud member of the Smartasscrew, MONSTER CLUB
Get your FIX today?