Scarlett, that is a decision that we all struggle with. But when you know, you know
Once the decision is made to find a facility, then it really gets difficult. Choosing a facility can be a daunting task at first. Just take it a piece at a time and you will find a good fit for Mom.
Randy gave you some good information. So much depends on the level of care your Mom will need and her ability to pay for that care. "Circle of Friends" is a fantastic program. But there are other options as well. My Mom and Dad were both in a locked unit. Dad did exceptionally well there. He had no idea the door was locked. There was a lovely garden to enjoy the outside and plenty of room inside to roam. Activities kept him busy and he didn't like to be too far away from the dining room
Mom had a little more difficulty.... but adjusted. If your Mom is ambulatory, with no other health problems, she will probably do well in one of these two types of facilities. If she has other health problems or is the very late stages of dementia, then she may need a nursing home. Her doctor should be able to help you determine the level of care Mom will need.
If there is an agency which will help you investigate the possibilities then use them. If not then ask friends for recommendations. Ask her doctor or a social worker. I started by calling facilities and asking for information to be mailed.... I also ask about waiting list. There are facility you can get into almost immediately... and other that might have waiting list as much as a year or more long. From that information I narrowed down my choices a bit. Then I started visiting facilities. As every question you can think of. Patient schedules, activities available, specialized diets, how they handle disruptive behavior, longevity of staffing, medication policy... and on and on. You will know the right and the wrong ones. This will further narrow down the list. Go to your state web site and check the facility for ratings and penalties. Then go back to the few facilities that are left at different times of the day. Even eating a meal if possible. Visit in the late afternoon and see if residents are sitting or active. My final attack was to ask family member, in the parking lot when staff was not watching, their thoughts about the facility. It's a lot of work and time... but it gives you a good insight into what the facility is all about.
It sounds arduous but once you get started it will make sense and go quicker than you expect
Good luck on your search and let us know how it goes..