You don’t give an engraved locket to a best female friend. That is something you would do for a girl you want to get with. Don’t change the locket. Keep it as a sign of changes you need to make:
(1) Be honest with yourself about women. If you like/love someone, don’t pretend to be a best friend. Best friend situations never turn in to romance.
(2) Once you make your move for romance (ask her out, flirtation, etc.), if she doesn’t respond romantically, move on. You don’t hang on in the role of bff. That is pathetic. It wastes a lot of time. And it saps your self image. Best thing to do is move on.

You should keep that locket exactly as is until you’ve learned these lessons, then once you have conquered that, throw it into the sea.