Flirting or Not?

I work with a girl, whom I've been dating for a year now, and I think she may be flirting with another coworker.

As in any relationship, we sometime see things that perhaps isn't there, therefore, I turn to you - the general public - for some clarity of thought.

My reason for thinking what I'm thinking is the following:

1) she was recently asked by "Joe", if she wouldn't mind proofreading a contract for him and after she did, she responded by saying that she liked one of the words he used.
2) After she asked her team (as she works in customer support) for passwords to a system that she used, he responded with his generic password, which she then responded by saying, "very original".
3) During a recent move from one office to another, I saw that she IM'd him asking if he knew the zip code to the new building...which makes me wonder why she'd go to him (after just meeting him), when her best friends work on her team (and she could have gone to them), and I work just a few feet away from her (and have been working here for 10 years).

These are the only 3 instances I've noticed but I could only guess there are more.

Is my mind getting the better of me, or is there something to be concerned about.

I'd like to hear what you think.