Good morning and welcome to the forum
@RobynG. I‘m so sorry to hear about your sister. It must be very hard for both of you to come to terms with the diagnosis - especially as she is so young.
I think you might find this factsheet helpful in terms of understanding Alzheimers -
Alzheimer’s disease is a physical illness which damages a person’s brain. This eventually causes dementia. Alzheimer’s disease is the most common cause of dementia.
www.alzheimers.org.uk
Also this one -
Gaining a better understanding of what it is like to live with dementia can help you support someone with the condition to live well. We cover topics such as identity, changes in behaviour, and the practical impact of dementia on the individual and carer.
www.alzheimers.org.uk
There are many factsheets available on the main Alzheimer‘s Society website and you can find the link to that at the top of this page - under your name.
If you haven‘t already done so it would be useful to get power of attorney organised.
I won’t add any more factsheets here as there’s nothing worse than being overwhelmed with information. The best thing for you to do is to keep posting here. Other members will be along later to give their suggestions and support. You will always find someone here to listen and to support.