Fraternity Fox's best shot against Pack Fox is literally her bullet curving. Pack Fox hasn't seen anything like that before and she might not initally be ready for it if Fraternity Fox immediately went for the kill. Unfortunately for Frat Fox, Pack Fox has seen it now and would be ready for it. So it comes down to overall skill and Pack Fox has her beat. A good matchup for both lethal ladies.
Also there is no way David hasn't rigged the ring to ensure his wife's victory if such a situation developed. Everything is accounted for, lol.