They are fighting in a restaurant in Manhattan. There are lots of civilians there, too. Neither is armed, but there is obviously a lot to use around them, from cutlery to furniture. Both are in character. They know nothing of each other prior to the fight.
Selene due to how long she has been alive has more experience and seems better skilled. Though in the fighting skill department it's very close. Gabriel is stronger though. Selene may be on par with him speed wise. It could go either way.
She may seem to have more experience, but Gabe has the experience of every other Law that was once in existence except for Yu Law, which evens out the experience gap. But still as he's a match for Yu Law in every way, all of Yu law's feats count for Gabe, and I'm pretty sure his speed feats trump Selene's, as well as strength. And since Gabe is great at not getting hit, he'll probably just dodge around Selene until she starts making mistakes, then capitalize.
Are you sure Selene's myriad combat knowledge, from her medieval skills to her more modern close-combat skills, can allow her to keep up with Law's extensive martial arts prowess and physical capability? He's definitely stronger but, at the point he's at here, she could be faster than he is.
Also, how do you think they would use their environments to their advantage?
You really think Selene is faster? None of her feats beat him outpacing cars or moving so fast that he perceives people already in motion and moving pretty fast because he hit them nearly standing still. Or the fact that he actually moves so fast sound slows down(shown when the Captain shouted Fire and it came out in slow mo) and is fast enough to dodge automatic rifle fire.