Was playing a lot of RE4 so this is what I got for now.
The loud-mouthed and arrogant Cozy possesses adult intelligence as a child and lives in her own house in Canterlot with no parental or guardian guidance with the exception of Twilight, who was tasked by Celestia to make sure her antics and shenanigans are kept to a minimum. She knows very well how to take care of herself to the point some adult Equestrians forget that she's still a child. She also works a job suitable for kids like her as a customer service rep for a large company, dealing with some of them and their backtalk as she backtalks them back immediately when it happens, but everyone still knows her as an annoying brat most of the time. She's more of a nuisance to society than an evil threat, but she most certainly can escalate up to that status without a problem. She often will flirts with older stallions on purpose which scares them off which sometimes results in her getting a lecture from either the authorities, Twilight or anyone else brave enough to go near Cozy excluding Diamond and Silver who are very good friends with her. Cozy will often use her cuteness and sweet talk to lure anyone in her home or another location to do her bidding whenever she feels like it or is too lazy to do it herself and they always fall for it. She loves practicing dark magic and messing with demonic tools and such and one day wants to catch her very own demon.
She's also a master at capturing people unsuspectingly, surprising them out of nowhere before they end up captured in whatever she brought with her, most notably stallions. However, with the recent influx of humans showing up in Equestria and arriving tiny at the same time, she's hellbent on capturing them for herself. It's unknown what she'll do to them, but Twilight always makes sure to find them before she does. She makes captured stallions massage her feet and do minor slave work in her house while belittling and dominating them before releasing them back into the public with their memories wiped of serving her so she can later do it to them again. Hoping to see humans in her home to catch after she heard one of her magical traps go off it turns out that it was just a few stallions that got to close to her house. Angry at this outcome she decides to still mess with them.