Hi Geean,
Wait, I’m confused. Is the workmate his girlfriend or are they two separate people?
I mean you could call him on it. When he mentions her name for the umpteenth time you could say, “Dude, you may not have noticed, but you have a major case of mention-itis.”
When he gives her attention at work you could pull him aside and say, “Dude, you’re being way too obvious.” Or, “Dude, we’re at work you know.”
Make him feel low grade awkward about showing attention to the girl.
In the meantime, make a list of why your friend isn’t so great and get a boyfriend of your own. Maybe your friend will wise up and one day look at you in a new light.
Best,
Inky