Thoughts based on info you have provided:
She should be looking a guys' boards as even the biggest girls' boards will be too soft for her.
As she is a beginner, a shorter board will be easier for her to handle, but you should encourage her to get onto something at least in the 150 to 155 range. Most riders of her weight doing the kind of riding she is leaning towards are on 158 +.
For a beginner, something with a mild rocker or flat profile would provide her with a nice forgiving, catch free ride.
Get it. Wax it. Ride it.