Outgoing girl becomes quiet and shy around me?

So I'm crushing on/flirting with a girl at work and I know for a fact she is single and is interested in me. However there is one issue: I see her talking comfortably with almost everyone we work with but when im alone with her she suddenly seems at a loss for words but still flirts physically. I'm assuming she's just nervous around me and that's impeding her speech. What would be the best way would be to get her to open up or feel more comfortable conversing with me?
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I already have her number and she communicates fine via text but in person it's like meeting a whole new person
Outgoing girl becomes quiet and shy around me?
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