Heather Benton

Corrected entry: When Lorraine follows Marty back to Doc's in 1955 and Doc goes to answer the door, he says to Marty (before opening it) that it's his mum. Lorraine must have heard them through the door yet she never questions it.

Heather Benton

Correction: Two possible reasons she never asks about it. First, she simply did not hear him. You're assuming she did, but there's no evidence of it. Second, asking questions would be tantamount to admitting to eavesdropping. It's rude to eavesdrop and so Lorraine would hardly give herself away by asking questions about something she wasn't supposed to have heard in the first place, and which would have sounded nonsensical anyway.

Phixius

Correction: Besides, even if she did hear him, so what? She knew she obviously wasn't "Calvin's" mum. She would have assumed his mum looked like her and Doc mistakenly thought that was who was at the door. But if she still decided to question it, I just gave an explanation that they would have used.