How do you take command of an aging parent?

does she have a power of attorney? you may have to consult an attorney who specializes in the aged

There are free resources out there to help. It varies by location but the "A Home for Mom" type outfits have good counseling on how to move forward. Small independant types can do a good job. We used one for my mother. They essentially get paid by the institutions they support. Nobody makes any money until mom is placed. There's quite a difference and complexity in getting insurance to pay for assisted living, nursing, long term care, etc. The insurance outfits selling long term care spent tons of lobby money in getting states to redefine the types of facilities so their policies wouldn't apply, hence lowered the likelihood of an effective claim (California was the pain for us). Just look up the term "Skilled Nursing Facility" and see how few of them exist anymore. That's the term in the policies the parents have paid into for years.

Capt Kevin is correct as well as SrA John. Getting up in years could be in her 70's or in her 90's. Check with a couple of local groups that work with seniors. An Elder lawyer would help with decisions on type of place, the Dr. would advise medically length of life, an accountant would help with financial ability. My mother moved into an independent living apartment 17 years ago and is now 102. The last couple of years she has had care givers because her abilities differ from those needed in assisted living and nursing care. She uses a walker and wheelchair, is legally blind, but does her own blood sugar test, gives herself insulin and plays the piano for sing-alongs usually for an hour or so a couple of times a month. She has PT and OT and goes to the dining room with the rest of the residents at least 4-5 times a week. There are a number of residents in their hundreds. The atmosphere makes a difference, and this place is active with outside and inside activities.
Write down what your Mom wants to do, how she feels, how she is medically and financially and then look for a couple of places. It should be her decision unless she is unable to make a decision. Visit senior centers and see what those places recommend by listening. Mom had a number of friends here and encouraged her to come. Since then, she has encouraged others to move in. Word of mouth is the best advertising - for the good and bad places to live.
Good luck - we all have times like this, and it may be harder as an only child, but you can get outside help that you trust to help guide you.