Sounds like a missed window here. In the post on breaking the ice / reducing tension (this one: " How to Break the Ice: 5 Surefire Ways to Entice Her," I talked some about the effect kissing on the mouth has on a woman's sex desire: essentially, it douses the flames of passion, unless executed perfectly and she's left wanting (much) more.
I wouldn't worry too much about how she's dressed. If you haven't seen the post on how to tell if a girl is horny, check that one out; a big part of it is, if a girl wants sex with a guy, much of the time she won't put in any extra effort. There was a female commenter I quoted on there who noted that she wasn't going to bother putting in extra time to get all dressed up for some guy she was just going to sleep with.
Essentially, if you're not going to sleep with her immediately after, in the same place you kissing her, don't kiss her. Wait until you get her alone - your odds go up dramatically that way (both of getting her back to your place, and of actually getting together with her when you do).