Namor doesn't dry up as quickly as some people think, though. Even outside of water, Namor isn't some weakling who gets wrecked easy peasy. And if Namor just came from water, he's good to go for this match, enough to take more than a couple of wins, imo.
Even at full strength, I think Barda's stronger, but at the least due to her mega rod has more offense (both in impact, and in very powerful energy blasts). Melee, she can go an *extended* bout with Diana (WW won due to using flight to have a maneuverability edge), so she's got the skills too. Defense, she's likewise at least as tough, and has armor on top to give an edge there.
Throw in a motherbox for regeneration, and she's got all the edges.
I give Barda the win, she was the leader of the Female Furies, has superhuman strength, stamina, is a great hand to hand fighter, and posses the mega rod. As mentioned before, she held her own against Wonder Woman.