shes really nervous around you & could possibly like you.
It can also be because she is nervous. Maybe it is because she likes you, or maybe it is just because she is shy and does that when she talks with everyone she really doesn't know?
shes trying to make herself look her best for you.
It's an indicator of interest that most women do subconsciously. Basically it's a sign she's interested in you.
it's an indication of attraction & availability, especially if accompanied by foot-pointing (when standing, her foot is pointing toward you) and wrist-exposing (showing the soft part of wrist).
guys have similar "tells" - they foot-point & hook thumbs into belt or pockets causing a sort of 'v' pointer to groin area.
next time you're at a party, have a look at the groups of talking people & watch how they're standing & what they're doing with their hands.
either she's interested in you or her hair is terrible .haha.
Usually its a sign she is interested or she thinks her hair is messed up.