The same thing happened to me when I was a kid. The lotions and creams made specifically for fading stretch marks never worked for me, but everyone's skin type is different so it couldn't hurt for your daughter to try them out. I simply rubbed the stretch marks with cocoa butter and later covered them with a little make-up. They faded, and now you can't even tell that they're there unless you're looking for them!
Stretch marks are certainly frustrating, especially since they never go away! I hope your daughter feels better about them soon :(