Two simple things really... I love you, and I'm proud of you.
And I know that those are important to me, because I find myself saying those things to my own daughter a lot...along with anytime she does something special, like goes out of her way for me, by telling her what a great daughter she is.
We had dinner with my boss and his wife both of whom I work with, and that night she said that my boss's wife told her how she can tell I am so proud of her, because whenever I talked about her I just light up and she loves asking me about her because I always have something great to say. I wish that my mother had the same reaction towards me..that its not just the words, but like you all also mentioned, that her actions, her whole vibe showed that she genuinely loved me and was proud of me, proud to have me as her daughter.
I look at kiddo, and for 17 years now, I'm constantly in total awe how lucky I am to have her as my daughter. She is who she is because she knows how much I appreciate and love her, not because she feels like she has to prove herself. She has way too much self-confidence and secure within herself for that! That's a gift that I wish I could have gotten. But at least it was something I was able to give.