The keys-thing can work, but only if it's a huge set of keys, and it's on some sort of a lanyard or a kutobon/handle that makes it a decent flail.
The between the fingers/improvised brass knuckles thing is useless. A woman fast enough and strong enough, and with enough grip strength to have the keys hurt the attacker more than they hurt her hand, to actually employ that effectively doesn't need the keys between her fingers in the first place.
Even if you're a ranked MMA fighter, male or female, ANY ranged weapon, or even one that extends your reach is much much better.