Triangle at work, don't know how to act

I work with a very nice woman, my reltionship with her is even heading to friendship. And there is a guy from a different department of our huge company. Being handsome and *rumours* not married, he was activily avoiding all the contacts with ladys at work but lately he started showing up in our office for no obvious reason - to chat about minor things, etc. Why? Is it a plan to make fun of us? Or could he really be interested in one of us? My colleague keeps saying I'm the reason he is dropping by, but when he comes I notice that he mostly engages in a conversation with her. Both of us like him. Should I give it a shot? Should I step back as she has been single for longer period than I am? But I don't want to step back... Do I even have any chances? I'm 9 years younger than him, and my colleague is 7 years older than him.

She keeps saying I'm the reason and that Fred and his coworkers are making fun of her.