"The little man's thread" LOL!
You've got 2 options actually.
1) If you know her very well, and have some ingenuity, take her to a place she likes, play a song she likes on guitar etc etc. But of course, if you don't know her well enough and think you do, this option can crash and burn spectacularly This is your classic High Risk, High Return option.
2) If you don't know her that well, or if she is like any of the young girls that Ris Low is a representative of, just buy the darnest most expensive thing you can buy without having to sell your kidney. This is your classic Low Ris, High Cost option.