Help? best answer 10points. plz?

Ive been working with this girl for about a month. She has a b/f and they have been dating for 2 1/2 months.. well me and her have been flirting and talking alot in the past, and just starting this week she has been avoiding me/ignoring me. Sometimes I look at her and I know she can see me looking but she looks away, and she use to just come up and talk to me.. not anymore. Is it because her and her b/f r getting more serious? or mybe scared that the fact that she likes me, but she is dating him? and her and her b.f are long distanced.. Need some good advice, and clarifiaction.. thanks (p.s i showed up to work with a hickey once, and she seemed jealous)