That's a pretty vain way to look at it no? Lol.

The only way it makes sense is if the song isn't about him.

"But you gave away the things you loved And one of them was me"

It's filled with references to his behavior hurting her. The writing and performance of the song may have been therapeutic, and that could be the reason it exists.

She wrote it for herself. To help her feel better about falling for a vain person. But that's just IMO.