Hi ,
My advice is to think about each of the 12 domains separately and write a list of the PWD's needs under each domain.
You have to make the case that your mother's needs go above and beyond what can be managed by staff in an ordinary nursing home. So, for example, under behavioural is your mum's aggression a risk to other residents? Would she need watching all the time? If she is mobile, has she any insight into what she can do? Does she constantly fall?
If you have any medical records or care records which prove your point then make sure you have copies with you.
If you pass the initial assessment and go forward to a CHC assessment then you must be prepared for the assessors to downplay each section. For example, my MiL could only shout yes or no but without any awareness of how she used the words. "No" didn't necessarily mean no and she could not express any needs to the staff in the hospital. However we were told that her needs under that domain couldn't be "severe" because she "could make noises" to express her needs. We argued the point vehemently and ensured it was noted by the staff nurse and my husband that we disagreed with the assessment on this point..
Preparation is the key. Try to get hospital staff, carers, etc to support you.
Good luck.
J x