I work in a fairly ordinary office set up with multiple departments. My colleague who I'm relatively friendly with is very attractive and clearly enjoys it. A guy who I also know a bit asked her out recently. Not only is she spreading it all around the office having turned him down, she s also been imo downright unpleasant about him, saying she wouldn't go near him with a bargepole etc. I don't know anything about him other than he is young and presumably single.
Your second post makes you sound slightly jealous, but I'm going to go with the tone of the first post and assume you're not and you just care about the chap. If she brings it up again, I'd just say 'I think you should stop talking about this so much. It's making things very awkward in the office' or similar.
You can stand up for the poor chap by telling her that "talking about Bob like that is really unprofessional". If she says "I don't care" then you have the optional tactic of saying "What, you don't care that you sound like a massive spiteful cunt?" - it's what I'd do, but you might find it a little too confrontational
I'd stay out of it personally. Lots of that goes on in my work place. Queen bee eventually got together with one of the blokes, when drunk on a night out they collectively asked for my opinion on the whole thing and I was, erm, honest about my thoughts on her behaviour generally (same sort of stuff your queen bee is doing). It didn't go down that well.