She had a recurring 'nightmare' [=she had the same bad dream many times] about losing her job.
Losing a child is every parent's 'worst nightmare'. [=the thing every parent fears most]
Mommy, I had a really scary 'nightmare'.
(..) So, guess what? I got off early and... Ta-da! I... I thought I wasn't allowed to see it. I changed my mind. As long as you don't have nightmares for a week. No, I won't. I don't get scared like that anymore. Oh, yeah? Not even of clowns? (..)2016 TvShow: Stranger Things Title: Chapter One: The Vanishing of Will Byers Season: 1 Episode 1