By withholding information.
By not telling her about her greatest accomplishments.
He has destroyed... no, he has not allowed her to develop confidence and self-esteem.
She does have the gift, but she doesn't know what makes it work.

And that thing about the Grim -- that was Sirius. Circling, drawing nearer...
She saw something, but didn't know how to interpret it.

About the Lightning Struck Tower, she said a bunch of little things.
One was about someone who dislikes the questioner... I forget the rest.
No one bothers to tell her which parts she gets right.