Posted before I finished writing -
Their sole focus seems to be their computer, the sun of their universe around which everything must orbit, including their wives & children. Everything else is background wallpaper compared to the number 1 love of their life.
It's difficult because my views are shaped on my experience, so another woman could tell you the total opposite, but my experience with men is that they generally don't make time for other females unless they're sexually attracted to them or think there might be a chance for at least some sex in future, maybe in the far future, if not a relationship if they're really invested in them. I think women find it a lot easier to think of male companions platonicaly, whereas men tend to develop feelings and other ideas a lot easier because they're more likely to associate intimacy with romantic relationships. There are exceptions to this, but this woman really doesn't sound like one of those exceptions. Unless she's a lesbian, I think she's acting foolishly. There's no way at that age I'd be associating so often, even online, with a man who has a wife and children. I'd be wary of it and even if I felt platonically about the whole thing, I wouldn't't want his wife to think I was something else or be involved in some kind of argument between them.
I think a decent guy would look at this situation and think 'She'll really attractive, but I'm not going to do anything outside of work with her because that might be sending the wrong message and it would be inappropriate'. If he was lonely, I think he would realise that it's best for him to make buddies his own age, not with 19 or 20 year old cool women.
I'm sorry, but I'm not sure if anything can really be done here. If he doesn't think your relationship is worth his time or respect, then I think you will have to emotionally withdraw from it yourself. I think you should try and put your foot down, for everyone's sake, but be prepared that he might not respond.