I have been IP very recently, I am 28 and had taken an overdose before my first admission so a similar situation.
The hospital itself is a safe space.
Some patients may be very obviously unwell (talking to themselves, shouting), initially this did scare me so your daughter needs to be prepared for this. I learned to zone out the chaos around me and focus on myself which helped.
In terms of practicalities, she will be checked (obs) at different times depending on what she needs. I think hourly/30 minutes/15 minutes are the usual increments. I sometimes had someone with me all the time but that is not the norm. They will check on you as you sleep as well, it can be a bit strange to wake up to a torch shining on you so maybe warn her!
The hospital I was in had fixed visiting hours - a couple of hours in the evening on weeknights and evening and afternoon visiting on weekends, they are pretty flexible though.
Time off the ward is called leave, depending on how your daughter feels and how the hospital feels she may be able to take leave to spend time off the unit. Initially this may be with staff or yourselves for a short period of time, but it will be built up to include overnight leave. So you may not always need to visit her - you may be able to pick her up and go home or out for a meal (much nicer :)).
As an informal patient she is in a good position, sectioning can impact on travel and jobs. Be guided by the ward staff about leave, staying informal is really important IMO.
There is not a huge amount of therapy that goes on, It is pretty low key, there are TV lounges, activities (I was on a woman's unit so the activities were very female - pampering, sewing, arts, DVDs, outing to local shops).
It is not like the films, you don't sit around doing group therapy, you don't have lots of talking therapy. The nurses/healthcare assistants are there if you need to chat, you have a review with the psychiatrist once a week, you might see a psychologist once/twice a week. Nothing is really forced on you, although you are encourage to eat / drink / wash / sit in communal areas.
It is a safe space though, somewhere to think and space to try and piece things together. Somewhere where the day to day stuff is sorted so you don't have to think about cleaning the house/working etc.
I had my own room, not sure if your daughter will. I read lots of magazines, my husband bought me a Kindle, on my most recent admission I did a lot of cross stitch (in the lounge - was a good way to avoid sitting in my room all day), I watched DVDs and I had my laptop and the internet (3 dongle).
Comfy PJs, comfy clothes - I wore leggings and tunics a lot, no glass bottles or aerosols, snacky foods are good. You are not allowed leads in your room but you can take them in and they will store them and charge your phone in the office for you. I had my straighteners PAT tested and used them there. Oh and you can shave your legs and pits - sometimes they watch you, sometimes they give you 5 minutes and come up for the razor. I took my Venus razor in with me - made me feel normal you know?
You also get priority for community services so things can be put in place for discharge, and medication can be started.
I hope this is helpful, it is very long! Hospital has been a large part of my care for the past 6 months.