Britta was always presented as flawed, but in season 3, the character started to enter a devolution in terms of development. She suddenly lost her intelligence and became a sillier shell of her past shelf.

What happened to Brita?

Britta's strength was her ability to see through him and understand him. She still does that. Britta ends season three not as an overly flanderized character, nor as an idiot who constantly fails – she ends it beaten down by her own friends. Abed tears Britta down in the finale, and she's never built back up.

Why does Britta hate her parents so much?

So what caused Britta to have such disdain for her parents and the “establishment?” It's likely due to her getting molested by a person in a dinosaur costume when she was young.