Well, having said all the intelligent, do it for you stuff.... I have to admit it stinks to be told you're no good. lol I was very nervous when I was in Ceramic DM. It was scary to throw something out there for everyone to see and critique.
We get our success in the eyes of others mixed up with our self worth. We have worth whether our writing, or painting, or music is good, bad or indifferent. But people can't separate it. It can be very painful.
It sounds like Crothian's teacher had this problem, since she had a problem with students more naturally talented than she was. It didn't make them better people than her, but it's likely it made her feel inferior.