The next night, Susannah has an epiphany: all her problems are being caused by the anti-seizure medication, regardless of the fact that she's only been on it for 24 hours. Susannah takes it anyway when Mom begs, but wakes at midnight with a start. She believes the medication is taking over her body and she is possessed with the desire to get it out. She goes to the bathroom and tries to make herself vomit, but can't because she hasn't eaten in days.
Susannah continues to feel paranoid and apply faulty logic as her illness spirals out of control. At this point she seems to lose sense of the chronological order of events, blaming her previous issues on the seizure medication even though she’s only been taking it for one day.
Susannah paces and finds herself on the third floor, where Mom and Allen sleep. She stands over Mom and strokes Mom's hair. Mom wakes up and leads Susannah back downstairs to her own room. She strokes Susannah's hair until she falls asleep, but Susannah doesn't sleep.
When Susannah essentially asks Mom for comfort, it shows them returning to a relationship in which Susannah isn't truly an independent adult. A much as she wanted to be in her apartment, Susannah is at this point incapable of living alone.
The next day, Susannah begins writing in a Word document that becomes a diary of sorts. She writes that she loves working, has to break up with Stephen, and that bipolar makes her who she is. Earlier that day she'd spoken to Dad about going back to school to study business, and Dad had counseled her to write out her thoughts. Susannah explains to the reader that some of what she wrote is a mess, but some is illuminating: she writes about needing structure and loving journalism.
Susannah's writing shows that she's very much grappling with her identity and trying to make sense of how that identity is rapidly changing. The fact that not everything she writes is strange or incorrect shows that there's still some of the "real" Susannah that's able to get out and onto paper. She's fighting a battle in her brain.
Later that night, Susannah walks into the living room and announces that she needs to break up with Stephen. Mom and Allen nod, but Susannah then announces that she needs to quit her job at the Post. Susannah leaves and comes back again to announce that she can't live in New York City anymore, by which time Mom and Allen look very concerned. Susannah finally realizes what she needs to do to fix her life, but then she falls to the floor with another seizure. She bites her tongue, spewing blood everywhere, and when Allen tries to open her mouth she bites his finger and draws blood. She comes to minutes later. Mom is on the phone with Dr. Bailey, scheduling Susannah for an electroencephalogram (EEG) to test her brain's electrical activity.
Note that everything Susannah announces are things that would, in some sense, help her grow up and achieve more control over her life under normal circumstances. Right now Susannah feels very out of control of her life and her identity, and is grasping for some way to define herself or find some agency. Allen's attempt to help Susannah makes it clear that her family is willing to put themselves in harm's way to help, even though Susannah isn't an easy person to help right now and is even somewhat dangerous.
On Friday, Stephen comes to visit and takes Susannah out for dinner. He takes her to an Irish pub, but it's crowded and Susannah knows that there are too many people, and that they're all talking about her. When Susannah cannot answer his questions, Stephen leads Susannah back out and takes her to another bar that's less crowded. Stephen orders for Susannah, but Susannah cannot fathom eating her chicken sandwich.
The people in the restaurant certainly are not actually talking about Susannah—her paranoia is growing. Notice that her paranoia is focused on what people are saying about her. Her illness is making her selfish and turning her attention inwards.
As Susannah and Stephen walk to the car, Susannah is gripped with the urge to either break up with Stephen or tell him she loves him. She tells him she loves him, and Stephen returns the sentiment. Later, Stephen notices that Susannah is smacking her lips together and has started trailing off and staring into space for minutes at a time. She explains that these were partial seizures and unnerving for everyone. Later, Susannah writes in her computer diary about wanting to "mother" Stephen, and she notes that talking to Dad makes her feel more sane.
When Susannah tells Stephen she loves him, it's implied that the urge to do so was brought on by her illness. However, the fact that she's not necessarily wrong (their relationship remains strong and loyal) shows that her illness, puzzlingly, offers her moments of illumination and even allows her to seem normal for moments.