Zipit Saddened for you and your Sis. She has endured a tremendous assault upon her body and mind. Antipsychotic medication+hypnotics (sleepers)+anxiolytics (Lorazepam etc) will all meld together and result in this typical presentation I am afraid.
Sadly as the fog of psychosis starts to lift and the patient begins to have some insight, they will have these awful feelings and say things that are upsetting and worrying. The realisation of what has happened is termed 'Crisis of Insight' (and though typically applied to patients who were on the older style antipsychotics and who improved in insight dramatically ob new ones like Clozaril) it affects many patients who have had a short term episode too. The staff must be made aware of whatever she tells you especially if it contains expressed thoughts of self harm, uselessness, lack of wanting to go on...You aren't breaking her trust because a sectioned person is deemed in need of safeguarding from themselves.
Have the staff reassured and shown you that she is receiving full anti side effects meds? She will also need daily reviews of her medication too. She needs to be encouraged to keep well hydrated to assist with the excretion of broken down meds, she needs to be monitored for food intake because psychosis burns a lot of energy even though meds will cause some weight gain.
Is she self caring yet? Bathing/showering? That is a sign of progress to look for. Maybe she'd let you brush her hair or style it? Spend time w/ her in short doses, the early evenings aren't the best time as I find patients that are very ill tend to be the most agitated and confused then. If she starts to express delusions try to gently distract her w/ the here and now- focus on what she can see, the weather, a magazine picture or a hand massage if she allows you to touch her. Don't get bogged down w/ delusional stuff. She needs gentle reminders that you do not share her beliefs. "The illness you have is called psychosis. The more unwell you become, the less ill you believe yourself to be". "I'm sorry but i do not hear that voice/see those things."
But only say this if she can cope w/ it. let the staff advise you on how to talk w/ her and approach discussion of her experiences. At this early stage delusions can be what they call Fixed with a complex Delusional Framework. This term refers to all the ideas/evidence connected to the delusion. For example if she believes that she is being persecuted she may have developed complex reasons why, evidence that it is happening...Think of everything you believe in. Then think of all the 'proof' you have for why you believe in it. She may or may not have the same for her delusions. Staff will 'test'' her through talking to her as to how fixed they are.
Some terminology-
Persecutory third person delusions are as they sound- something or someone is persecuting her in her belief. An 'Idea of reference' covers things like thinking people/somebody on the TV is talking to you or about you. A delusion is a belief or sensory experience that has no external trigger/stimulus. An illusion is where you misinterpret something 'real' like a shadow becoming somebody in the corner.
Ask staff to explain all the symptoms to you. They should be doing this. After a visit, ask to speak privately w/ a nurse to debrief you. Tell them of all concerns. Make sure you speak to them away from the hullaballoo of the office/nursing station. Make them pay attention to you.