I discussed this sort of thing with my wife a while back. She feels safer riding her bike than she does walking. When she's walking, she assumes that any person she encounters is a potential threat, and is generally aware of everyone around her. She has taken a fair bit of kickboxing training, but would more likely rely on running and screaming as a defence. "Keep fighting, no matter what" were her exact words. She's 130 lbs, but is strong and not above a little physical contact - she once laid out a competitor during a soccer game. She also believes strongly in multiple groin kicks and the eye gouge.
On the bike, she worries less about the nutjob on the sidewalk and more about the Escalade making the blind lane change. That said, she doesn't like to ride her bike too late at night, and will request that I come and collect her if she doesn't feel safe. She avoids the MUP, as she feels it is too isolated, even during daylight hours.