I’d say that if anyone in Equestria deserved the garden ornament treatment, it was her and Tirek. I’m less certain about Bugbutt, but maybe my love of sultry supervillainesses is clouding my judgment. My biggest problem with it is that Discord and Glimglam weren’t right there with her.
 
Glimglam used time travel magic to destroy Equestria. Successfully. Multiple times. Because she had a grudge. She got cheap forgiveness because the script demanded it.
 
Discord got cheap forgiveness after going on multiple reality-destroying rampages and a betrayal because the audience liked de Lancie’s voice acting and he was good for ratings.
 
Cozy Glow is a malevolent little creature and does not seem to have a better nature to appeal to. She has zero backstory. Maybe she was born bad. Maybe she was abused. No one knows and the show writers worked very hard at sidestepping the topic. She doesn’t look fixable or salvageable. From a utilitarian perspective I can see the argument in favor of euthanizing her before she can do more damage, little kid or no. But, see. Glimglam earned the same treatment many times over, as did Discord. Discord’s basically Nyarlathotep. Maybe he’s not killable by any means the ponies have access to. But there’s no excuse for letting Starlight Glimmer live, if a little kid got the petrification death penalty.

Exactly I still hated that the writers make her a villain with no backstory she does deserve better! I know I’m going to get some hate by Bronies for saying this but I don’t really care what they going to say the Bronies themselves are also assholes to Cozy Glow which is complete bull crap!

That poor filly deserved better. It’s a fucking travesty, what they did to her.