The 14-year-old only learned she would meet the Superman cast, as well as director James Gunn, when she arrived at the BBFC offices after being confirmed as the competition winner.
Elsie said: “Missing a day of school for that was awesome, the best excuse.”
“In the moment I was trying to keep it cool because I didn’t want to embarrass myself, ” she said, but the day after was “going round to all my friends saying ‘guess what? guess who I just met?'”
“I don’t think they really understood the severity of it. It was quite a big thing, which I didn’t even realise until I found out I won, she told the BBC.
The mega-fan, who said she had “probably” seen Superman films at least 50 times, also attended a fan preview of the new movie, which hits UK cinemas on Friday.