I take it to mean that he's done his girlfriend wrong, and when they break up or maybe just before they break up, she's wishing that someone else loved her.
And I also think the line "And now you wish that you meant something to somebody else" has a double meaning.
I think she might've tried to get back with him, and he wouldn't take her back, so now she's just wanting someone to love her. The very end of the video makes it seem like that too.