Yes, there is a lot wrong with a small woman carrying a pocket knife to use for self defense.

Knives for self defense in general are a bad idea. One, you’re escalating whatever situation you were in to a life and death situation. Maybe it already was one, maybe you were just going to get beat up, maybe the person was just being intimidating and nothing was going to happen. The second you pull a knife you’re upping the stakes by a lot. Two, knives have next to no “stopping power”. A common thing you’ll hear from people that have been stabbed in altercations is that they didn’t even realize they were stabbed. If you wound them bad enough they might die later (unlikely with a small pocket knife), but the knife is not likely to help you in the middle of the altercation. Third, and most importantly, you’re giving the other person access to a weapon. As others have pointed out, the biggest problem with a smaller, weaker person without any knowledge of fighting carrying a knife is that an attacker can take it away from you.

Combine these points together and by trying to use a knife in a self defense scenario and you’re creating a situation where you’ve escalated a situation, maybe stabbed someone which isn’t likely to stop them in the moment but is likely to make them very angry, and then given that person access to a knife.

Pepper spray or a taser are much better options