When we talk, she glances at my lips and twirls her hair. How should I read that?

We work closely together. She glances @ my mouth and twirls her hair. Even though that's a sign of flirtation, could she just like twirling her hair? She wears low riser, revealing jeans which sometimes when she bends I can see and when she gets up, she pulls them up and her shirt down. I'm not sure if she doesn't want me to see or does but doesn't want to look obvious. And what does it mean when she looks at my lips alot?