In the sense that she seems to have not been navigating that dynamic as smart (or alert??) as she could be. Just sort of underestimating the meaning/influence/effect of a jealous spouse, unintentionally entertaining shark moves from what appears to be a messy dude, etc.
Thanks for contextualizing with the recent death in her family and her general feelings of loneliness and depression. I think that, plus the way she's affirmed her love and commitment to you/your relationship, are key assurances here. Looking at her behaviour in the context of this (and also how you don't seem keen on ending your relationship), I think she's worth a benefit of the doubt here (although, perhaps just one lol).
The job honestly sounds healthy for her given what she's been feeling recently. It sounds like she's just wanted to fit in, make friends, feel a renewed sense of purpose, do well (which she must be, since you mentioned she passed her necessary certs), etc.. All healthy things for someone who's been feeling cooped up, depressed, and dealing with relationship rockiness and the recent loss of a loved one.
But the downside of that is... in trying to fit in and adjust to a new crowd and life she's kind of slipping a bit in the correct way to manage this particular coworker. If you don't mind me asking, is she fairly young and/or personality-wise kind of impulsive???
Anyway. As a few of us predicted, you communicating was very helpful here. If she was sort of just auto-piloting to fit in at work, your conversation was hopefully the wakeup call she needed to course-correct moving forward.
Tbh, I'm actually most concerned about her being able to sustain and enjoy her new job, lol. If she intends for this job and her friendships there to be sustainable, she's got to see the risk in NOT establishing proper boundaries with this or any dude, ESPECIALLY in the context of a jealous spouse and it bothering you as well. Regularly hanging out with dude(s) one-on-one should not even be an option, especially after hours. She needs to keep it to groups and keep it professional.
But contrary to what you guys agreed on, I'd even go one step further in that if there's going to be an opportunity for you to meet him, maybe you should see if you can push for dude to bring his wife as well. Like meet them as a couple. There's still something that smells a little off to me about the partners (meaning you and his wife) only meeting the coworkers one-on-one. There's still opportunities for a little smoke-and-mirror bullshit there if one partner knows/sees more than the other. And not only is there a lot more vibes to be read from observing the dynamics within and between couples, but it provides your girl more cover if dude truly is as trifling as he sounds. Meaning, your girl is clearly already on the wife's radar too so the more often she only ever sees your girl as part of a stable, ongoing, couple and NOT checking for her man the more it should (hopefully!) diffuse weird energy from their end, and allow your girl to continue enjoying her work and work friendships in peace.
I also wonder whether there's sufficient benefit to having some deep revelatory talk with his wife about the hookah thing... If your girl just tightens up her shit at work moving forward, puts some more boundaries up when it comes to dude, and you guys as a couple only interact with dude and his wife as a couple, I think that should render things stable and sustainable moving forward.
Just my 2 cents though *shrug*