Solanacae
Crowing
That Sunday rule was interesting!you may find this useful if you don't already know it
https://www.allotment-garden.org/allotment-information/allotments-the-law/
I'm assuming the council is the landlord from what you said
While I never want to have a mental illness, I sometimes wonder how much they understand or realize what they are doing but can’t stop themselves. I guess it varies from person to person. Still, I know from working with my own children and those that I taught that people tend to live up to the expectations you have if them. Treat them like they can’t do anything right, they’ll fail every time. Let them know that you recognize their potential for doing good and acknowledge their efforts (despite their failures and mistakes) and they will respond towards you positively. They may not be perfect, but it makes such a difference for them to know you’re in their corner. They still have to be held accountable for their mistakes and you have to set limits with them, but that can actually help them trust you more in the long run. I would hate to be in C’s position, if she feeling like she can’t do anything right and everyone hates her.C reminds me of a toxic former coworker who once let slip she struggles with a personality disorder. Researching the disorder later, the phrase, "persistent lack of self love" stuck out. I figured the only way to counter that would be persistent compassion. As much as she damaged my career, I can find compassion for someone who deals with that kind of pain.
From then on, I started every interaction with a soothing sentiment: "Wow, you did such a great job there," or, "That's awful they didn't recognize how hard you worked!" It was like a switch flipped. She still found ways to cause chaos, but rarely with me, whereas before I'd been a main target. Somehow she never figured out what I was doing. The only side effect was throwing up in my mouth while complimenting her screw ups. Dishonesty isn't my cup of tea.
If you have a goal to reach with C before you part ways, I highly recommend this approach.
Examples would be, "Wow, your bird netting is...going to make birds think twice." And, "Gosh, it must be difficult dealing with all the ways people are accusing you of stealing." <--Kidding. You have to really make her feel seen. She knows she's screwing up but can't stop until someone sees her. I worry for Henry.