Give away 3 day passes with facebook ads, when they go to opt in for the pass, upsell them with $30 for 30 days. Next you can upsell them on personal training and offer them a "$200" discount off a training package if she trade in her 30 day pass worth. you guessed it $200 (example figures). Another way I've heard but never tried is bootcamps. I use to work in a gym years ago. Multiple ways to do it tho, this is one.