katy, as I noted, leading a lady's heel turn is generally not that easy. You might want to see if there are posts about it in the archives; I think there's one discussion right now on heel turns in foxtrot, but I'm not sure if it's on quite the same thing as here. Someone else will probably be able to explain things better, but here's what I remember about it drawing on notes about heel turns in other dances.
I believe that to lead a lady's heel turn the man will usually have a faster rise so that he will already be Up when taking the second step. The man's second step also tends to be shorter than for other figures and has a stronger rotation because he needs to come around the lady while keeping her basically in place. I know there's a lot more you can talk about including correct swing and sway and such and *if* everything's done correctly the lady shouldn't have a choice but to close her feet into the heel turn. As long as no one says I'm totally wrong here
hopefully these two points will help a bit -- the faster rise and the shorter, more strongly rotated second step should be signals that you're being led into a heel turn. But hopefully you'll get some more responses with additional, maybe more detailed, information.