"So she bought a wooden recorder (it sounds nicer!) and they didn't have a descant. It has a range from middle C to one octave and a note."
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If the recorder's lowest note is a C, then it's either a soprano (descant) or a tenor. The tenor is unlikely, as it's quite expensive.

I just picked up my most unsatisfactory descant and was able to play an octave plus six notes on it.

I suspect that if Joy can only get an octave plus one, then she is simply not playing the high notes right. Chances are the problem is with her thumb. More than that I can't say without being there.

I think she should find a player or teacher and get a little expert advice on the matter.