Name what happens at night.
Getting up for the bathroom. Wandering. Waking at three unsure where she is. Each one needs a different kind of help, so start with what her nights actually look like.
Awake overnight and live-in are not the same.
An awake overnight caregiver stays up and responds. A live-in arrangement includes sleeping time and breaks. Ask which fits the nights she has, not the nights you hope for.

Start with the hardest nights.
You do not have to cover every night to get relief. Two covered nights a week can change how the other five feel.
Make the mornings easier, too.
A short handover about how the night went means the next person, or you, is not starting from zero.
At Pink Glove, we talk about the nights before we plan the days.
We will ask how often she is up, what she needs, and what coverage is available, and explain the costs before you decide.