Also, never ever ever use fabric softener on towels. It ruins them by covering them in an oily thin compound that nullifies their ability to absorb water. And it takes so much work and many washings to fix them.
Get some wool laundry balls and whatever scent she'd like in essential oil, add a couple of drops to one of them, or 1-2 drops to each ball if you want to be fancy.
If that isn't enough for her, pour white vinegar in the fabric softener compartment of your washer.