Not a female, but...
.... in MA, around 30 years ago, my dad's cousin had a close brush with a serial rapist. He was posing as a flower delivery guy, complete with van, and his ploy was to pretend he was lost, and ask if he could use the phone to verify the customer's address. My dad's cousin actually let the guy in the house. Luckily for her, her German Shepherd (named "Pup", and the dog was usually a big baby) keyed on this guy and started growling.
This is when the light bulb went on for her.
The guy asked, "Does your dog bite?" She said, "Do you want to find out?"
The guy left.
My dad's cousin called her husband, at work; he, in turn, called the cops, who came out to the house in numbers. They told her this guy had raped four or five other women, using the same ploy.
They also told her, living out as far from town as she did, that she really should buy a gun and learn to use it, due to 20+ minute response times. Yep, Massachusetts, in the late 70's, cops told a woman to buy a gun.
Sorry to veer off on a branch, but opening doors can be a real risk, even when people look like they might belong.
And, to reinforce one of my favorite themes, dogs are good, and big dogs are even better as deterrents.