He has a group of work friends that is close to, and his best "work friend" is a female colleague around my age. I have met her a few times and she always seemed very nice and warm. I won't lie and I was suspicious initially but she is married and has kids too, and I let it go because he can obviously be friends with whoever he wants. It's just a bit grating to hear your DH and another woman being referrred to as the "dream team" in work even if this is just a work related term.
I met her yesterday by chance, and said hello as we obviously know each other a bit and she was very different. She was polite but seemed uncomfortable, so I assumed that she had just been busy or stressed. I told DH that I had met her and that we'd chatted and noticed that he tensed up and changed the topic fairly quickly. Normally this wouldn't make me wonder but somehow it did because they had both been strange.
DH and I have been going through a bit of a rough patch recently. Nothing major but everyday stress really. He's definitely been more short tempered and irritable than usual, though he has always had form for it, but I have probably also not been blameless either. So maybe I am just being paranoid because of this. Now my insecurities are back and I'm not sure if I'm being unreasonable.