This is actually a predicament i may eventually face. For the most part i was never a onegina PL, so i was never latched onto just one dancer and didn't ever really have this issue, or it was just one-way (her perception). Now i have an ATF like no other before, so right now i don't mind and even immensely enjoy just dancing with her. But yet still i would like to dance with some old favorites and some hot new blood every now and then. I guess the good news is that the ATF doesn't strike me as particularly jealous and she'd probably not rather put all of her eggs in one PL basket on any given night.
So besides coming in on a day that she doesn't work because there is pretty much no way that i'm not hitting her up when she's working, i might actually have to beeline right to another girl i'm interested in first when i go to the club or be proactive about who you dance with. Or not hold her seat before she joins you or if she does join you and when she takes any type of break (bathroom, DJ, whatever) from front room action and another girl (hopefully a girl you're interested in) joins you. If she does get to you eventually, and at this point you still enjoy getting dances with her, throw her a few bones and get some dances, just quite a few less than you normally would. There's no need to shut her down completely, unless you don't care if you ever see her again at least in the intermediate term. She should definitely notice, but just tell her you're taking a bit of a break for now. When she walks you back, tell her that she doesn't have to be stuck with you and if she falls in to a rut, she can always find you again. In the meantime she can try working the rest of the floor or any other regulars and you might do the same.
No, there's no easy way to do this, but just remember that as overstated as it is, it is just business to you and her. No need to get emotions, real or whatever, involved in this. She'll get over it sooner or later, and most experienced dancers can figure out where this is going (a clear and definite change in your "relationship"). Just don't ever feel guilted into doing something you don't want to do, especially when you have done nothing wrong, for real.