That's good and all, but realistically in a no rules anything goes situation, it's best you have a weapon with a good reach. Just because she prefers to use her fists doesn't mean everyone else has to do the same. An aluminum or metal bat is honestly a good weapon in this case, they're actually quite light, but hits really heavy. It can't be blocked by a knife, nor can they really block it with their limbs without taking fairly bad damage to their own limbs.
Also, it's weird how the knife users here are using their knives so inefficiently. Why are they all trying to go for the head, one of the hardest places to land a blow? They have a fucking knife, knick, slash, or stab any body part that's most easily reachable. Wound them slowly, whittle them down, let the bleed as the fight prolongs.