<human>: I am a married guy (39, my wife is 38, married for ~17 years).  I have a good friend I work with that is a girl, she's 35, and we've worked together for about a year.  

The issue is that at work, and when we're in a group (or when her boyfriend is around), she acts like we barely know each other.  However, when it's just the two of us hanging out ... or her, her sister, and me (we swim together for training) ... or even me, my wife, and her, she's really awesome.  

My problem is that this hot/cold friendship makes me feel like she thinks being close friends is wrong.  It almost makes me feel guilty about it (which my wife says I have nothing to feel guilty about, I share all my thoughts/feelings with my wife).  I am a happily married guy of average looks (at best), and totally NOT her type, so the probability she's interested in me is pretty close to 0.  She's really friendly with other guys around her bf, so I don't think it's a jealousy thing either.  

Any thought on what's going on?

Could you distill the essence of the text into 1-3 sentences?
<bot>: Close friend is only close in private, but is almost dismissive when more than 1 or 2 people are around (or bf).  Not sure what this means.