> Even I, average looking girl, walk with a knife everywhere and I am trained how to use it to kill

I can guarantee you that if you ever end up getting sucker punched by an adult male, you will at best get dazed and not know what's going on, and at worst knocked out cold. The knife is giving you a false illusion of safety. It would only ever be really effective if you were the attacker that pulled out the knife on a victim with the intention to inflict harm. The first to strike usually comes out on top.