Throwaway because, well, throwaway.

Girlfriend and I have been together about a year. She works in criminal law in an office that is about 90% male. Her coworkers make up most of her social group - she's there 50 hours a week give or take, they were the first people she met when she moved here, etc. I've never had a problem with that as she doesn't spend one on one time with any of the men, and we don't have any problems in our own relationship that would make me question.

So we're out the other night to celebrate with these folks - pretty big case everyone's been busting their ass on finally came out in their favor. Anyway, we wind up, everyone is getting up to go and one of her partners comes over to hug her goodbye. He shakes my hand, hugs her and tells her good work, and as she's hugging him back she says "I love you, thank you." Off he goes. Off we go.

I didn't make an issue of it because I didn't want to come across as bothered when I'm not sure there's anything to be bothered about. She didn't hide it but she didn't flaunt it either, and there's nothing else in our relationship to gripe about.

Yet, I'm bugged. Insight?

ETA: This resolved itself quite nicely Sunday evening, thanks for all of the insight Reddit. Appreciate your conversation as always.