this is why nice guys finish last, they just sit back and wait until the end of time.
she seems physically comfortable with you, you're just wasting time. i can understand how certain situations wouldn't make the best make-out spots, though. so set up a good situation. rent a movie instead of taking her to one, you can do a hell of a lot more alone on the couch than you can in a stadium seating environment with thousands of people around. pick a movie that has a romantic subplot, isn't too cheesy, and has doesn't have a story that requires full attention. something where you pretty much know what's going to happen and there's more emphasis on you two rather than the movie itself.
go for a kiss on the lips, my guess is she'll surprise you.
after that it's just a matter of rounding the bases. now THAT'S the fun part.