That recording makes my speakers mad, I can't really tell anything she sings, but you are having some debate over her grammar. I'm an English major and I'll tell you, most people don't mind grammar errors in songs.
If only you could tell me it’s okay and me listen cos it already is
^^ that does make sense if you think of it like.......
"If only you could tell me it's ok, and have me listen, cause it already is".
Whatever, we all know what she means.