Sister Krone grew up on a plantation just like the other characters we've met. She entered the story as someone who came to aid Isabella in keeping the plantation under control. Krone was in awe of Isabella and genuinely looked forward to working with the youngest mama hailed as a genius among her peers. However, Isabella brushed her off from the start, telling her in no uncertain terms that she was basically just a pawn and should do as she's told. Not exactly something you'd want to hear from someone you admire.
When Krone finally realized the extent of Isabella's loss of control and that she was actually careless enough to allow the secret of the plantation to be revealed, she saw this as the perfect opportunity to rise to the top and usurp Isabella's "mama" position. How quickly admiration has turned to intense hatred. Krone's first reaction was to ship out the children who knew the secret, which was procedure, but Isabella convinced her not. Krone then set out to put her own plan in motion by finding evidence that the kids knew the truth so she could take it to the higher ups. This proved difficult as her intimidation tactics didn't work. She went as far as to sow seeds of disloyalty among the children by raising issues of trust. She tried to get them to spy on each other, but Gilda, the child she tried to use, proved too loyal to her family.
The next best thing Krone could think of was the age old "if you can't beat them, join them." What better way to bring down a common enemy than with an alliance? Krone still had her ulterior motives of course, but if she could get the kids to let their guards down enough to reveal what they know, she'd essentially be killing two birds with one stone. Getting rid of Isabella and the kids. She made herself available to the kids, answering any questions they had about the outside world, the trackers, security etc.
This tentative alliance would be short lived though. Isabella chose that exact moment to implement her own plan. Everything Krone did was with the intention of being a mama. If you're an indispensable asset then you're safe from becoming food. Isabella produced a letter from headquarters with Krone's dream. The opening of a mama position and Isabella's own recommendation. But despite everything, krone wasn't stupid. She knew this was a trap, but when you play chess with a master no doubt you'll be eventually outclassed. Isabella made it impossible for krone to refuse. Despite her lack of evidence Krone still did her best to convince the higher ups that Isabella had lost control of her farm but it was to no avail. However, before she died we're shown that she made her own preparations, because even in death, bringing down Isabella was her greatest wish.
Krone was an individual who fought for nothing but her own, personal, agenda. She played nice when she had to play nice, scheming and plotting continuously while trusting no one but herself. She fully realized the evil of her own actions, and how the twisted system she was brought up in made her this way, but still carried on nevertheless. Her goal was ultimately just to survive, to be on the "Eat" part of the food chain. Krone was never reformed. She was unapologetic for the things she had done and would have done given the chance. Her last play was also selfish. She didn't care about the kids actually escaping other that it would bring down Isabella. Krone didn't allow herself to be swayed by pretty words of hope, or the fact that these were children. Thats what made her an interesting villain in my opinion.