Question: Why did Polly get a panic attack in the middle of the night?
Answer: If you listen to her yelling when they try to subdue her, she yells out "I'm ugly". This is most likely stemming from earlier when Angelina's character makes a comment about Polly never finding love because of the way she looks.
Question: Why was Daisy keeping the old chicken dinners under her bed?
Answer: It is very common for bulemics, as Daisy was, to be embarrassed by the food they eat. It's only natural for her to want to hide her eating habits. She states that when she gets 5, she has to throw them away. You imagine the smell of 5 rotting chicken carcasses under your bed after 5 days. Her father seemed to be a very powerful man so therefore she has some special treatment and is allowed to indulge a little. As long as she's eating, they'll let her have the chicken.
Answer: Polly freaked out because she had seen Suazanna kissing her boyfriend earlier that day. Polly realised that is something she will never have.