So the HR girl at my work came by to tell me my phone was ready and told me to go pick it up from the IT department. We walked together to pick the phone up. It was about a 10 minute walk I really like her and I think she likes me as she was acting all giddy like girls do when they like you. Well, she works a level below me and right under me. The building is huge but our desks are close together. I just don't think I will cross paths with her again. She left me her email, desk phone number and cell phone number and told me to call if I had any problems. Should I call her on her cell phone and ask her out? Or is that not appropriate since we work in the same building? It's a huge building though but I am afraid if she declines and I run into her again it will be awkward. What should I do?