Gym girl - what is to be done?

Hi Guys,

I attend a gym regularly, three times a week. There is this hot young babe which I am working right now. We had already three dates, in which I blew some chances, and did not kiss close. I assume I could have kiss closed her, I am not sure. But I could have progressed much farther at the time.
Since the AFC in me did not allow me to avail myself of the windows that opened (and I remember them opening), I am now in a more difficult situation. At the time, I thought that since I was seeing her regularly, perhaps missing some opportunities at escalation would not be that important. I can see now that I was wrong.

Anyways, she has a boyfriend, but agreed to date me - that baffled me.

But, after the three dates she flaked the next two dates. I assume I was too aggressive and possibly frightened her away, saying we would go out and "have fun", that she should dress "sexy", etc.

Anyway, since then, I have been proceeding slowly, but always advancing. Now, we regularly hug each other tightly and every now and then I kiss her directly on the cheek. Besides, I am able to lay my hand in her thigh for 5 seconds, etc.
She has started half of the hugs we had, and I have started all kisses on the cheek so far. And she always reciprocates my kiss with another one of her own.
Once, I grabbed her hand and we stayed with our fingers intwertwined for about 10 secs. I have already smelled her hair a couple of times, etc.

Recently, wondering about the flakes, I assumed I had to build up some Comfort, and not ask her out on a full-fledged date. And then I asked her out to a cafeteria nearby, to which she immediately agreed. And we had good conversation, which I used to then throw little things like: "-if you were mine", etc, etc.
I never allowed myself to be placed on the friend role. I am not her emotional tampon, nor anything of the sort. I have been always Escalating kino, albeit too slowly, and she still blushes every now and then, depending on what I say and do.

Two days ago, I could see her looking at me over the gym, and mirrorring my body at a distance.
Question is: this boyfriend stuff seems to be dragging things a lot. This whole stuff has now lasted about 6 months. I can see I advance, but the pace is too slow and tries my patience. I am almost giving up, but only to see her always becoming further interested. It looks like almost an elementary school crush on her part.
It doesn't look like she will give up this boyfriend. Fine. But since I have other girls, it would be enough for me to have an affair with her. She is hot! I tried the BF destryer pattern, but is not being too effective.
What do you guys sincerely think I should be doing in order to accelerate this and have an affair with her?