Linda
I remember vividly the day we first heard Lewy Body Dementia when my DW got her diagnosis about a year ago.. Like you I researched and found some alarming and awful things to expect. But as things settled a bit, I learned that evertone's journey is different and not every LBD person will have all the possible symptoms. And the severity of symptoms varies as well. My experience thus far has been pretty good all things considered. My wife, about the same age as our sister, still has a wonderful sense of humor. We laugh a lot, even at some of the frustrations of dealing with LBD. There are things she cannot do, but there are lots of things she can and enjoy.
A couple resources I found helpful were LBDA (Lewy Body Dementia Association) and the Lewy Body Canada websites. These are managed by people who have or are living the Lewy experience.
There others here on the Lewy journey who might share some of their experience.
Keeo singing those hymns and I am sure you will fing ways to bring joy to your sisiter.