As a Beatle's fan do you think Run For Your Life is one of their better songs or a bit of an embarrassment? I feel it shows why both words and music usually make a song. Peace to all, except Cynthia it says.
Michelle is a great tune with next to no lyrical content, just I love Michelle. Anything other then a love song would have come into conflict with the melody in my view.
The problem about your lyrics, for me, is we (the listener) don't know enough to agree that your friend's ex deserves to be called selfish. You have provided no reason for the break up or whose fault it was, or even why she should consider the feelings of her ex, other than he's your friend. This may sound a bit harsh but if you are writing for the song to be heard by strangers you need to consider the song from their viewpoint and how they'd hear it.
The break up of a relationship is always difficult which is why there are so few songs about it. Most songs are written/sung from the point of view of one of the parties to the break up. Most of them seem to be country songs for some reason.
The most famous song about a break up sang by a third party is Hey Jude. Its addressed to Julian and basically says, chin up son, things will get better. Even then John thought it was about his impending divorce from Paul. Which just goes to show how one person's words can mean different things to different people, even people who are close. The song didn't require the listener to take sides with either John or Cynthia. Most people, including a younger me, didn't realise what it was about until many years later.
Finally, some of your lines I really like, including the coaster line, its just the judgement on your friend's ex I find difficult to accept. As its the chorus it is an a major obstacle to me liking the song overall rather than just the music and some of the words.
Hope this makes sense,
Keith