If someone knocks on your door as a MESHULOCH or COLLECTOR, but you don’t know the person. It might be dangerous to let the person in. Are you wrong for refusing them entry into your home?
You do not have any obligation to answer the door! Unless you know that the person is trustworthy, you should not let him inside your home. Although there is an obligation to give money to a poor person who asks for tzedakah, the fact that the person knocks at the door is not considered as if he asked for money. Therefore, a woman that is at home alone etc. does not have to answer the door to people collecting money, if she is afraid that there is a danger involved.
On the other hand, this should not be understood that we shouldn’t give anything to the people collecting money, we should give, however it should be done in a way that is safe.