Girls, female friend opinion?

I'd really like to know if you think my female friend might have feelings for me. We've worked together for 2 years now. We're really close and she trusts me quite a bit. As a background she has told me that in general she is a shy person. We usually have boundaries up since we're "friends" and she's married but I've noticed that she's touched me on the arm when i make her laugh or I got slapped recently (in front of others) for teasing her. This is only when I catch her off guard with a joke or teasing cause she is usually reserved and composed. But at other times she seems distant so I can't figure it out. She has called me a really good guy friend before, but then the other day when I returned from vacation she sent an email saying the "office" missed me (i don't have any other friends in the office). So does anyone think she might have suppressed feelings or is being friendly?