If she grabbed a wadded up old stiff piece of tissue paper off the floor, I'd might worry (but it wouldn't be about HIV).
If she got the tissues from the cupboard, I think it's safe to say you're in the clear.
The price of tissue paper is not so high that massage parlor workers would want to take used tissues, wash, iron, and fold them and restock them in the cupboards. I just don't see that as possible.
It really wouldn't have mattered if she would have gotten it off the floor. It's not an HIV risk.