How do I know if this girl really likes me or just likes to flirt?

[Will these roads ever end?]

So I've found that the girl I reaqlly want to talk to( but am too afraid to do so) has in fact a boyfriend. By just looking at her Facebook page. She added me a long time ago when we had a group task together (I'm 22 and we both study marketing) but I despise Facebook so I never really check it. Well, the signs she gives me are- so I think) an indication that she feels someting other for me than for all the other people she talks to. I just need to figure out what. I never really talked to her alone. Only once, but then I felt quite awkward, I was afraid and couldn't be myself. She noticed it I think.
The times I come across her are sparse. One time we walked out of class and though she has some female friends she walked side to side with me and I was walking behind my friends and... I don't know I looked at her and got this strange vibe, she looked uncomfortable too. Then, other times when we walk almost right at each other she often greets me with a wide smile or she ignores me but I see that she saw me. She's almost never alone though.
The thing is, I am interested. But if she has a boyfriend that's a no go for me, I know how I would feel in his position so no. Also, if she broke up with her boyfriend or is about to I am very shy. How can I be myself around her?

[tb]

Just relax around her, for now you can only be her friend so that should make you more comfortable. Try to initiate conversation with her and become a bigger part of her life. In time who knows what will happen, she may no longer have a boyfriend and then you can take that opportunity. Some of the best relationship/marriages began as the couple being friends so being friends with this girl is a good start.