That, right there, is the best trick you can ever do for any girl.
If you want a slightly more extensive answer, here's what's up. Yes, you love magic. Yes, she's probably somewhat amused and/or entertained by the fact that you like magic. Notice I said "like" there. Truth be told, if you're anything like half the guys on these boards (myself not excluded though
), she probably hasn't even begun to grasp what it means to you and how enthousiastic and passionate you are about your hobby. Chances are that she might not interpret your intentions correctly.
From your post and your question you appear to be rather young, and as such (though I might be wrong here, and I apologize in advance if I am), I'm biased to say that your performance skills might not yet be fully up to par. Because of this, I'd shy away from trying to create a "magical romantic moment" through the use of magic.
Why not try to create a "magical romantic moment" through the use of romance instead?
[Edit]
I forgot something. In case you decide to be stubborn and go with the original plan, pick something self-working or very low on sleight of hand, since you don't have a lot of time to practice. Then, do
everything in your power to make it about
her. Really, take your time to sit down, and think about
exactly what you want to say to her through this gesture. Make
absolutely sure that she will not interpret it as "look what I can do". Then, after you've shown her your magic, still take her out to dinner (and as final advice, this is also a guaranteed win as a make-up in case she does interpret it incorrectly).
