Low self esteem?

I'm worried. I had depression for a año and eventually came to terms with it. Anyway my friend is now who I am concerned about.

We had this leadership talk yesterday, because we're seniors siguiente year. Anyway, the teacher was like to everyone "Everyone is interesting.." o something like that.

Anyway my best friend turns to me and goes "I'm not interesting, I'm boring." And I just went into shock. What should I do? I asked her later and she kept saying she was boring.

What can I do to help my best friend's low self esteem? Because I don't want her falling victim to depression like I did.