I know somebody like that FS. Whenever somebody is feeling particularly happy, she always manages to say something seemingly benign that is hurtful. It'll be a little comment, that looks like a compliment, but isn't, like, "How nice that you can still pull off that hemline even if it is really out of fashion."

She looks really confident, but when you really get to know her, you find that she has really low self-esteem.