A Swiss Army type folding knife has a good chance of "folding" in a self-defense situation and cutting the fingers of the user...it could be used in an emergency to slash, but stabbing will fold the blade into one's own hand. Locking-blade folding knives are much better but usually lack the hilt which will prevent the hand from slipping down the handle and onto the blade. Unless one knows where in the attacker's body to slide a blade most folding knives will break. A repellent spray is fine if it can be properly deployed. But if I were a woman I'd also be carrying a small handgun and practice drawing and firing at close range (proximity is what most male attackers seek) because a potential attacker may well also be armed with a projectile weapon...and may be so highly incensed at being sprayed that he/she will shoot with a gun from a distance.