It sounds like a descant (also known as a soprano). It will be about a foot in length. This is the size that children usually learn on, so most music shops will stock descants and this is what they'll give you if you ask for "a recorder" without being more specific. The other common size is the treble, but this is considerably bigger and in F. Bigger still are the tenor and bass, and there is also a smaller size (sopranino, also in F).

The descant is fine for folk music, playing in D and G is easy and A maj can be managed. You get the relative minors of course, including Am as the instrument is in C. Other keys are possible but the fingering gets more complicated.

She should be able to play higher notes than the top D, but this is done by "pinching" the thumb-hole and blowing harder, both of which take practice. Presumably she's working from a tutor book, this should explain how to get the higher notes. If not, she'll need to find a player to show her how - a local music shop might be able to help. Quite a few teachers, even if they're not musicians, can play a bit of recorder, as of course can many kids of primary school age as it is the usual "starter" instrument.