Well, IMO you'd have to start by knowing whether they even made it home that night. It's pure speculation that they even made it there that night. Even the police didn't think the crime scene looked right. As one of them stated, "It was like they were just raptured". As if they had just disappeared.
As you've said, we don't know how any of them would have reacted. So we can't speculate how Sherrill being a mother, would have reacted. What if they had a gun to her head, or to her daughters head. Think she would have fought back then. I think the chances would have been slim if that were the case. But one never knows how a person will react, when they or a loved one is facing a perceived certain death. Fight, Fight, or, Freeze. Those are the three reactions people have to a perceived threat. One person could have easily taken all three women. It's not like it would be the first time in history that one person gained control of more than one other person with a perceived threat.
Bottom line here is, no one even knows if they made it home that night. Just because their cars were there and their purses and personal affects were there, doesn't mean that someone returned the things to the house. Stranger crimes have happened. JMO.