Pre-Flashpoint Kara should win quite comfortably. The only times Jane has been hit as hard as Kara is going to hit her is when Odinson tackled her through a adamantium and vibranium coated door, Cul powered Destroyer hit her once or twice before help came, and she recently got hit by all the worthy hammers at same time. Cept now those punches are gonna be hitting her at the same speed or faster than she currently uses Mjolnir to blitz with.