Hello
@Cathmay and welcome to the forum. I am sorry to hear of your sister's diagnosis.
My late husband was also diagnosed at 58 - and also found it a relief to finally have an answer as to what was happening to him - especially as he'd been out of work for a couple of years, unable to perform well in interviews and losing confidence. His ability to express himself or write coherent sentence were among the first skills to deteriorate.
I was told by the memory consultant that symptoms do progress more quickly in people with young onset dementia. Everyone is different though and there is no set pattern - but in our situation the quick progress did happen.
As soon as the diagnosis came we did the practical stuff like getting our Wills and Powers of Attorney sorted - and from then on we just took each day as it came, concentrating on what could be done, adapting ways of doing things - and gradually letting go of what was no longer possible.
It was a stressful experience at times, as is the case for many with a diagnosis, regardless of type or age - but we had many happy experiences along the way too - and for the most part we lived well with the disease.
Do keep posting, we are here to help and support one another. You are among people who understand.
Edited just to add that this link to information on young onset dementia might also be of some help -
Find out what young-onset dementia is, including the causes and symptoms, and how it is diagnosed and treated.
www.alzheimers.org.uk