Just to add my minor $.02 for your consideration....
If you get a stun device of some kind, definitely get her a Taser C2. It enables one to engage the suspect prior to physical contact. But, if you miss with the darts (has happened to me twice dealing with rapidly moving targets) you still have the device to use as a direct contact stun device. Or, in the case of one dart impacting, you can complete the circuit by making contact with the end of the Taser on the suspect's person.
If you go with a personal defense spray, get something in a ballistic stream. It would have a better chance of making contact with the suspect and not the user - a windy day could have you coughing worse than the suspect if you are using a traditional aerosol carrier. But I have seen people fight right through an entire can of oleresin capsicum painted upon their face with almost no ill effect, so be aware that it
may not work.
Bottom line, there is no 100% reliable non-lethal self defense system to carry, but by being mentally alert and in tune with your environment gives you a great advantage and could keep you from being targeted at all. (if more people existed in this condition, I am certain there would be less victims in the world. the wolves look for easy prey) Also, have the mindset that if one is attacked, you are not going to go down easy. Fight, fight, fight, and
never give up.