I strongly disagree that this is nothing.
I don't have any good advice, especially since she is so young. When she's older, I might encourage her to say "Thank you, I also just passed my green belt test in tae kwon do" or, whatever (girl scouts, music lessons, soccer, spelling, science, whatever she ends up being into).
My brother had those same looks (along with super-long eyelashes). We BOTH remember, clear as day, the random elderly cousin who would always say "Oh hello there! You are too pretty to be a boy!" and then turn to me and say "Hello". I could just hear her saying "Hello muddy-headed blue-eyed yet olive-toned ugly tomboy." He heard "You look like a girl."
I _applaud_ your concern. I realize what they are saying is seen as positive, but the effects _could_ be anything but.
My brother and I both still have issues with this, though our mother certainly seemed to agree with her. At least, she would verbally to her face--and she still tells my 35yo brother he should shave (he is clean but very grungy "not pretty"), he has such fabulous coloring. And she told my husband she couldn't believe anyone would marry me. And she has never accused me of having fabulous coloring (dh does, though
:, and he is soooooo happy our kids got that olive skin so they don't burn like lobsters like daddy