The Lasting Power of Attorney guidance has lists of things within both financial information and health care which may help you. She may also want to consider an LPA depending on what her prognosis is.
Have a look here:
www.gov.uk/government/publications/make-a-lasting-power-of-attorney/lp12-make-and-register-your-lasting-power-of-attorney-a-guide-web-version
and here (individual guides linked at the bottom)
www.gov.uk/government/publications/make-a-lasting-power-of-attorney
Fnancial decisions
Financial decisions might be about:
opening, closing and using your bank and building society accounts
claiming, receiving and using your benefits, pensions and allowances
paying your household, care and other bills
making or selling investments
buying or selling your home
You don’t have to own your own home or have a lot of money to
make an LPA for financial decisions. For example, if it’s hard to manage your bank account or bills alone, you may want someone to help.
Health and care decisions might be about:
giving or refusing consent to health care
staying in your own home and getting help and support from social services
moving into residential care and finding a good care home
day-to-day matters such as your diet, dress or daily routine
To this I would also add as others have said:
Who do they want with them as they are actually dying/becoming more frail - this may not apply but in some cases patients will in effect go into a coma/ spend more and more time sleeping. Some people prefer to be alone others want only very close family, others want friends and so on. It's good to get a direction as to their feelings about this now and especially people they really don't want there.
Making a will
Directions as to who should get specific items (Aunt Adelaide to have my jewellery; Uncle Tom to get my books).
Listing in one place all their investments/bank accounts/ financial matters (it's common for small investment funds to be unclaimed because beneficiaries never knew they existed)
Funeral plans/preferences Burial or cremation, who do they want invited, donations to a paricular charity in lieu of flowers or flowers, sombre or celebration, and so on.
Online/Social media - do they want any online presence (Email, Facebook, LinkedIn, Instagram etc) deleted or memorialised. Do they want to give you passwords to these accounts so you can access them (especially for email) or delete/close them down after their death?