possibly the brightly lit profusion of stray hairs. possibly the strong (clashing) reds and greens. Her hand could have been softened a little. Looking closer there's a slightly odd combed or brushed effect on her eyebrows. I only mention these things because you asked - they're things that some may find fault with.
Also this type of challenge is always tough in voting.
I just looked at the voting pattern - those low votes are simply mindless
I totally agree with Maggye here. I'm not often inspired by portrait photography but this image is wonderful in its vibrancy. The composition and lighting are good and it is a shame that it didn't score higher.