Starlight was sent hard to the boulder and Twilight's face filled with horror and a bit regret when she saw that Starlight's horn had broken off. The force of her powerful magical blast and the impact upon the boulder was stronger than she had realised. The look on her face fell as Starlight's horror grew into frantic fury at her opponent.
Twilight used her magic to telekinetically get up Starlight as she then had them leave the dark future that she had sent them to so that she could go all out without endangering anyone in the past. She didn't trust Starlight to play dirty and be willing to endanger innocents just to make Twilight falter; she had made clear that her mask of doing things for a more equal future was just that: a mask.
She then had then sent back to collect Spike and got the Sonic Rainboom to go off as it was supposed to before returning to the present. She then burned the scroll and then used Starlight's own spell to collect her Cutie Mark.
"Let's see how you like having your Cutie Mark removed yourself..." Twilight said shaking her head as Starlight felt her life left her as her Cutie Mark was forced away from her. She could only weakly groan as she tried to get up on her knees.
"Spike... Take a message..." Twilight told him as she had to inform Princess Celestia and all her friends about this...
A special trial was set up before Princess Celestia and as special witnesses Twilight had managed to track down and collect Sunburst and Starlight's own father. They both looked disappointed at Starlight who growled from the defendant's stand with her Cutie Mark put in a special place inside a jar while next to her; Starlight's public defender had to tell her not to make it worse for herself.
Twilight and her friends were all called as witnesses whose glances towards Starlight went from just extreme disappointment like Fluttershy's to outright anger like Rainbow Dash's.
Twilight and Spike made their testimonials about the horrible timelines that Starlight's petty actions created and how she refused to listen to reason. However what was really telling was the testimonials collected from the residents of 'Our Town' who were looking for a new name for their home.
"...She kept claiming that getting rid of our Cutie Marks would be our choice but those that didn't want to part with them... She kept practically stalking us to share the virtues of being equal with everyone else..." spoke one villager.
"She pretty much encouraged everyone to shun those who wouldn't part with theirs..." spoke another.
"She disregarded any ideas of electing our leaders. 'Why would we need elections when everyone is clearly equal and everyone has their own role to play?' Those were her words despite the fact she was clearly in charge in her own self appointed role..." bitterly spoke another.
Each testimony pretty much tore down Starlight's claims of wanting to spread true friendship and equality when all she was doing was making sure that she was in charge of her own cult; she led all the sheep while keeping her Cutie Mark so that she would be the only one special and never actually practiced what she preached. It revealed that she truly was just a self righteous control freak who never got over a friend moving away and took it out on Cutie Marks as a whole.
The jury didn't spend long handing down a verdict.
"...I can only hope that a term in the dungeons without your Cutie Mark would help you realise what kind of mare you are... As you feel as your forced others to feel without a part of yourself... " Princess Celestia handed down her sentence sternly.
Starlight fumed in her dungeon cell blaming Twilight, her friends and 'the ungrateful flock in that town'. Still convinced that she hadn't done anything wrong and that she only had the best intentions. As an added bit of irony; the food that she had to eat were the same kind of bad pies that was served at Our Town during her time as leader. The ones that she avoided eating herself and had her own stash of actual edible food.