What's the footprint of a 15 gallon tank?

Since she is so little, I might suggest putting her in a smaller space. Could you divide the tank in half?

Also, bumping the temps up a little, like to 94F seems to increase appetite by increasing metabolism.

Pre-scent for about an hour before offering prey and try feeding at night time, when they are more active.

Lastly, make sure she has two identical hides from which to choose.