I guess it would depend in what part of town I was in. Typically I don't drive in bad parts of town. Although I would be more worried about someone hitting me as I was changing the tire because we have a lot of bad stupid drivers. Since I am a woman, I would not change a tire at night without a man around just in case a creep tried something weird, or if I really needed help just doing the job.
I would call someone to help me if I was alone at night with a flat tire.