This is a very difficult situation. I'm so sorry you find yourself having to deal with it. You obviously have a lot of compassion for her and it bothers you to cause her distress, but at the same time, you do need to have that option to do what's right for you.

ITA with Beth that she is probably terrified. Having gone through something similar at age 30 with a spouse to assist, it was overwhelming then, I can't imagine doing it at her age and alone.

I'm not sure if anybody else mentioned this, but some states have a "council for the aging" or some other organization that's designed to help seniors. Maybe if she doesn't seem to be able to get a handle on the situation within a few months, your state has an organization like that you could contact on her behalf? Given what you've written here, I think I'd feel more comfortable involving a third party assistance rather than trying to help her directly.