My coworker pats my butt and tells me how much she likes it

I work as a personal trainer at a large gym. To be a trainer you have to be proud of your body and want to help others improve their fitness. Most of my co-workers are pretty touchy feely, and it's usually fun and not a problem. But one of my co-workers I feel she goes a little overboard. Pretty much on a daily basis she will swipe her hand across my butt or she'll give it a little squeeze or pat. That's not really a big deal for me but sometimes she'll pat it really hard and say how much she likes it. For example, she'll pat it and say cute booty. I consider her a friend and we hang out after work with friends, and we go dancing on the weekends, but I prefer not to be alone with her. I know she's not a lesbian but I think she has tendencies. I don't want to complain or make a big deal about it. I want to work at the gym for at least a few more years, and it doesn't bother me that much and it kind of feels good. My butt is kind of ticklish. Sometimes it embarrasses me when a lot of people are around. Most of us are pretty touchy feely and it is kind of normal at my work. The guys are pretty chill. Sometimes they will squeeze your butt a little but mostly they will just rub your shoulders or massage you.

I hear a lot about harrassment, and the gym posts signs saying keep your hands to yourself, but I don't think anybody pays attention to it. I would never complain unless I felt threatened or if it interfered with me doing my job. My question is, is it normal in work environments to be close with co-workers, kind of touchy feely? I've only worked three places. I worked at a restaurant, another gym, and all three environments have been pretty touchy feely, and most of my friends say they're pretty flirtatious with co-workers.