Keeping her interested

Alright, I'll try to make this story as short as possible.

A few weeks ago I was out with some friends who brought with them this HB10 who might very well be the cutest girl I've ever met.
Even though she knew I had a girlfriend at the time (and she apperantly has a bf) she kept giving me ioi's, following me around trying to talk/spend time to me, she even took my hand while walking through the club (her initiative), dancing with me etc, and always keeping eye contact with me even if she'd dance with some other guy.
All in all, I see this as she's pretty much interested in me, I ended up dissing her and she ended up with some other guy that night (who was not her bf).

I never tried to game her much that night (I didn't have to anyway lol), got her number and msn and all that crap anyway.

So last weekend we were out again, she told me she was with some friends at some other place, so after a while I went there (with a short time constraint), and this time I figured I'd push-pull a bit in order to see if she's interested or not.
I got there, sat down next to her and we started talking about whatever, i told her I'd have to go soon and she told me she was leaving early tonight which I said was fine, however she'd miss out alot of fun if she'd go home, but she still said she'd go home soon.
We kept talking, I got closer and did some kino and some games and whatever, and after a while she gets even closer and places her hand on my thigh and crap, but eventually I told her I'd have to get back to my friends and that we'd see eachother some other night instead, but instead of going home she came with me to the other place but I didn't spend much more time with her there except from some talking and dancing (I was out with my friends and my gf, so yea~).

After this, we have pretty much been talking about random crap basically every day, she writes to me as soon as I logs on, she texts me, and she's suggested that we meet and hang out.
I've used alot of BF Destroyer routines on her, and gotten her to admit that she doesn't know if she likes him and doesn't know if she wants to stay with him etc etc, and I guess it's been going pretty well all in all.

A few days ago I broke up my LTR and I thought this would be the perfect time to get together with this chick, but she didn't want to go out this weekend as she had planned spending time with her bf, but she would still consider it (still a no though).

Anyhow, enough about the background, what I need some pointers about now is what to do?
After every conversation we have, I get a stronger feeling that I'm soon about to get friendzoned for real, as our conversations gets more and more dull (even though she still keeps interest and still writes to me every day), and today she told me that she could never cheat on her bf again (when we were talking about me seeing other girls after my LTR), so getting alot of mixed signals here.

So, any overall help is very appreciated, I know I should probably freeze her out completely, but as we don't know eachother very well at all and haven't even k-closed yet, I'm afraid that by doing this she will lose insterest instead.

Also, another sidenote, I've negged her quite alot, which seem to have worked fine, but she oftain sais stuff like "oh im not pretty/funny/whatever" (seems like she's got low self-esteem even though it's obvious that ALOT of guys are interested in her), so the question is, should I just stop negging her and try something else instead?

But like I said before, any help, pointers or opinions are very much welcome!

It's important to be well calibrated when using negs. Not all girls see themselves as hot. And like you said, the pretty ones can sometimes have low self confidence. I would ease back a bit, as it doesn't sound like she's full of herself... Hope that helps!