Like stated above, just be different then most of the guys in there. Definately work on your approach and comfort in conversations Like Smooth noted. This is her place of employment though, so scripted stuff and situational openers aren't really going to make it happen IMO.
I managed to game a 30 year old personal trainer into her cell number for non-work related purposes as well as emailed pics(semi-nudes) when i went back to college(im only 20) and I was possibly going to get a lay when i went back home for thanksgiving but she got back together with her husband

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What seemed to work for me was starting off on professional grounds and just getting to know her by asking questions during a fitness orientation and being cocky funny when it came to her trying to sell me personal training sessions. From there it just turned into casual conversations(a lot of convo, i worked out almost everyday that summer) and i would enlighten her about my weekend of binge drinking and blacking out. I think what lended to my partial success was the fact that i made her feel young again through my stories so if there's any way that you can possibly do this to your particular PT i would advise for it(Their profession is based around getting fit and looking young, if shes older take advantage of that and make her feel good about herself).
My logic might be flawed cause of the specific circumstances of her almost getting a divore from her husband and wanting to feel young again by turning to me but i hope you can gain something out of it.