Bad idea.
Very, very bad idea.
What others said: you generally don't say you love someone unless you're in some sort of relationship (long-term friendship at the very, very least and even that's risking creeping the person out). Further, you really should just tell her rather than trying to concoct some elaborate plan to show your love. Finally, assuming the band has other people, this is going to be even more awkward for them and also for her.
Someone also mentioned "Fortune favors the bold.", but they got it wrong. Be bold: just talk to her. Trying to kind-of-sort-of tell her with a song is not being bold, it's just awkward.