Ok, I'm sure this is an idiotic question, but is it possible for her to play it wrong in such a way that it sounds out of tune? I'm sure that the instrument was out of tune. But I don't know (from here on) how to tell if she's playing it incorrectly or if it's a tuning issue.
It isn't an idiotic question and the answer is potentially yes but unlikely. It depends on the number of strings and series of notes she is playing. When it is a little out of tune, notes may just sound a bit sharp or flat but it can be so far out of tune that she is actually playing a different note. For example, she may consistently place her fingers a bit too high or a bit too low, which can mimic a slightly out of tune string. Although unlikely, she may also consistently finger the wrong notes in such a way that every note is shifted higher or lower. However, if the series of notes that she is playing include open string notes, then the melody will sound different.
It may be easier to just download an iPad or android app and tune it for her yourself. You will most likely only have to adjust the fine tuners (turn knobs attached to the front bottom end of strings). You can tune it using pizzicato (pluck the string with your finger) rather than with the bow.
The bottom line is there are so many ways for her to play a piece of music incorrectly that you want to take the tuning issue out of the equation.
