The problem with carrying any sort of weapon is that one may feel the need to use it - and if one does, the weapon is not enough, one has to also have the mental state to be nastier than the predator and that is pretty hard to instantly conjure up as we are not predators. Any predator has worked themselves up into an extreme mental state and it is very difficult to match that - this being so, an attack on a predator that doesn't work will further enrage that person ... fill in the dots ..
The best defense for anyone, male or female, is to regularly take a self-defense course, such as Karate or Judo, make it part of their home life routine.
First action, in any encounter, is to take two steps backward, this removes one from being held or attacked. And to me, the best defense on camino if concerned is to unclip the hipbelt - then the pack can be dropped in a moment and one can run - running away is a good thing to do. Everything in a pack can be replaced so it is unimportant.
I knew a wonderful old guy ran a boxing gym in a poor area. Any youngster joining had to learn to run a mile before he would teach them, his ethos being that if attacked one should run away but only a fraction faster than the attacker, after half a mile or so look to see if the pursuer were out of breath and gasping and if so they should stop and turn round, punch them hard so they fell down, and then stroll home.
The thing about carrying a weapon such as pepper spray is that it is no good unless it is held in the hand, thumb on the trigger, as attacks can be super-quick and unexpected - does anyone really want to do that for 500 miles?? Really?
At night one can carry a bright torch - flash it in the eyes and you have a five second head start when you run away and if one really feels the need to carry a spray, well, it doesn't matter what it is as the aim is to hit the eyes (don't you hope they aren't wearing sunglasses) so many sprays would do the job, hair spray, deodorant spray, even WD40!
Just about a quarter of a million pilgrims last year, and we heard of how many incidents? Five or so? Now look at the crime stats for any town of a quarter of a million and compare. Exactly - we are safer out there than in any town in my country that I know of.