I have no real experience dealing with an ex girlfriend who hasn't crossed the "restraining order" line yet but is still paddling around in the shallow end of crazy.
Sigh. Sorry you are dealing with that.
I'm glad you are wise enough not to be posting too many details online. I will assume truthiness in that you have more weird backstory you are not at liberty to reveal. If that is the case?
Could tell her you are aware of her activities. In front of witnesses. And tell her to cease and desist and to please respect that. (Maybe you do it by certified mail or something rather than in person. Whatever it best in your case.)
Go home, write statement summarizing this was done, take you and your witnesses to notary, have notary watch you sign statement, get notary to notarize statement. File it safe somewhere. $10 for the stamp is cheap
for your piece of mind.
She doesn't have to know this bit. It's for YOU, should she start something else and try to change the name of the song if she chooses more crazy behavior.
Hopefully it will come to naught but should you have to start gathering evidence for a restraining order -- there ya go. First item in the folder and you aren't starting from ground zero scrambling around.