honest truth, she sounds like a birdbrain. thats a very simple minded joke, and i actually like it a lot! in online dating ive received the best results by sending the same exact message to many women. I like to call it, 'fishing with dynamite'. try different wording next time.
at any rate, it might be cool of you to not try and be funny directly, but say nevermind, its just one of my many pickup lines ive been trying out

doesn't seem to be working. whats some of the most ridiculous pick up lines youve gotten so far?
that would probably lead to more interesting conversations and openings for humor...but as i said that girl sounds like a bit of a birdbrain. good luck to you with her!