I'm not female, but I have been the victim of random street violence that left me hospitalized with amnesia. That happened to me not on tour, but when I was in a busy middle class university neighborhood with two of my friends.
With regard to safety while touring I think it's more important to worry about traffic. If you feel vulnerable to violence I'd say just carry mace or a knife if it makes you more comfortable (a knife is a useful tool to have anyway). As a female you may be at higher risk of sexual violence, but on the flip side people are more likely to trust you and help you out along your tour.
I did once wake up to a family of bears within arms reach of me while on tour. That was kind of terrifying, but they just sniffed at me and walked away. A can of mace might have made me a little more at ease in case the mother bear had become aggressive though.