You need to go over and look at her house. Walk around the entire exterior, in daylight. You are looking for "bee traffic" If a swarm indeed entered her home and established itself, you will see bees coming and going through some type of gap or opening. Be thorough in your inspection as an established hive could be anywhere.
Now, consider this, the bees could be yours or from a feral colony in the immediate area. Be nice and volunteer to help your neighbor if they ask for your help.
And as others have already mentioned, yes, bees are attracted to lights at night.
Another thing, quite often people will grossly exaggerate the amount of bees they see. Perhaps there were far less bees than said, maybe not, but be aware for potential exaggerations.