I would recommend borrowing another bike to try first.
You could also try pushing the seat back and putting a longer stem, but it sounds too small. 15 Women’s hardrocks are quite short
My wife is the same height and recently changed from an 04 15″ Rockhopper to a 16″ Men’s Kona Steely. It’s about 3 inches longer and puts here in a much better position. However, it really depends on the relative length of your arm’s, body, legs etc, which is why it’s important to try a few different bikes first.