Writing the song is only a small part of the equation. Erin McKeown wrote a very nice song. Someone else did the hard work of turning it into a hit. Sounds like Erin is jealous that someone else is more capable than her at creating hits.
Maybe Erin should learn from this and focus on what is her strength - songwriting. Sell your great songs to people who are more capable of turning them into hits. You can make a nice living that way.