While I still think abduction is far and away the most likely intention(whether it be ransom or otherwise) allow me to play devil's advocate for a second and provide an explanation for why someone would be abducted even if it were not the original intent.
Say this individual broke in for other means. Whether it be robbery or even expected someone else to be in the house. Then they run into Nancy and are like oh crap, I did not expect this. The intruder could be thinking in that moment "What do I do? I can't just flee and leave her here. She'll call the cops. And in a neighborhood that is not very dense and late at night, I'm likely going to be one of the few cars out here on the road at this hour, I'm going to stick out like a sore thumb when cops patrol the area, so I gotta just grab her and take her with me to prevent her from calling the cops."
Again, I still think abduction was likely the intent here. But by chance it wasn't, that could be a reason why it ended with her being kidnapped anyway.
Say this individual broke in for other means. Whether it be robbery or even expected someone else to be in the house. Then they run into Nancy and are like oh crap, I did not expect this. The intruder could be thinking in that moment "What do I do? I can't just flee and leave her here. She'll call the cops. And in a neighborhood that is not very dense and late at night, I'm likely going to be one of the few cars out here on the road at this hour, I'm going to stick out like a sore thumb when cops patrol the area, so I gotta just grab her and take her with me to prevent her from calling the cops."
Again, I still think abduction was likely the intent here. But by chance it wasn't, that could be a reason why it ended with her being kidnapped anyway.