A good mastermind always has a plan “B,” or maybe even a plan “C.” Starlight had many layers of defense.
 
Fluttershy had discovered that night that Starlight secretly still had her cutie mark - but the leader always wore a skirt, or a dress. So all she had to do was unveil it in front of the town.
 
The opportunity finally came, and she struck! - only to find out that Starlight had a second layer of defense!
 
“How dare you try this cruel prank on our wonderful leader!” Double Diamond yelled as the group quickly turned angry in Starlight’s defense.
 
Starlight’s heart raced - first with terror at her cutie mark being revealed - then with glee as she realized her plan had worked: if any pony ever tried to reveal her secret, she knew the town would come to her aid!
 
“Oh, my deepest, darkest secret is out! It’s all because of a terrible injury I received just a few years ago! The doctors said I’d never walk again - but I miraculously healed! - but not all the way…” Starlight feigned, “Will my friends still accept me despite this terrible injury?”
 
“Of course, Starlight! This is Fluttershy’s fault!” Party Favor responded.
 
It would take quick thinking for Fluttershy to expose her cutie mark now.
 
==
 
Edited this as per a suggestion.
 
I don’t always take requests, but if I like the idea I may do it.
 
Addendum: Made a cloth version ‘cause I’m a stickler about realism :P >>1105514