My INFP sis thinks she's stupid. I totally disagree and would like to help her. I'm an ENTP, so i'm more motivated and louder than she and well, have managed to be a bit more successful than she is.

My question is, how can I help her gain self-confidence? I keep telling her how she's better than most and how she's really not dumb, but that doesn't seem to help. Is that a hidden agenda thing?