DUDE! She was into you! She didn't go back with her mates I would have taken this as a massive clue that she obviously likes you. You should have kissed her, you don't even need some cheesey line just go for it.

You should believe that you look good all the time, as for small talk just say whatever is in your head as long as you are not worrying or thinking to much about what you are saying this way you'll seem genuine (because you are being genuine!). Improv will help this too