Is there perhaps something about the wheel she doesn't like? Is it tilted, or small, or rough? Maybe post a photo of the wheel in its place to see if someone might notice something that could be a problem.
I have a bucket wheel and I noticed my hedgehog didn't run on it when it was leaning ever so slightly in such a way that would make him slip out.
Or, I saw someone mention this on here before-- maybe a little flour(?) sprinkled on the wheel will show if it was used in the night? Don't know if you've already tried that.
here with my Mecki-- born 2/12/19