How has Angeline's mental health diminished since the beginning of the novel to the next time that we meet her with Artemis?

Juliet comes to Artemis stating that his mother is having some issues. He stops what he is doing and goes to the door of her room. He hears giggling and his mother talking to "Timmy", his father. When Artemis walks in, his mother thinks that Artemis is her father and that she is on her honeymoon. Artemis realizes that his mother's madness is getting worse. She is sitting with her wedding dress on and has a facsimile of his father, made from his wedding clothes, sitting next to her. Artemis goes along with his mother and pretends to be her father. They converse as such for a moment or two and then Artemis leaves her as she is with the thought that he has other business to attend to.