Welcome Leigh. Sorry you needed to find us but glad you did. This is a great place to learn of the experiences of others, get support, and vent when necessary. We are all have this disease in common.
Please associate Grandma Moments with the good moments, those moments of joy, that you can still have with your Grandma. The devastation you feel is caused by this horrible disease. If you focus on the disease progression as a whole it will make you nuts. If you take one moment at a time, enjoying those good moments with grandma, it all goes a little better. You can't eat the cow but one steak at a time you can enjoy the entire cow!
There are two books I can recommend. One is "Creating Moments of Joy" by Jolene Brackey. This helps understand how to create those moments of joy and hang on to them. The other is "Coping with Alzheimer's: The Caregiver's Survival Guide" by Rose Oliver and Frances Bock. This book helped me to focus my thinking on the positive.
The inability to walk is just one of the many loses an Alzheimer's patient will go through. There are general guidelines in the stages of Alzheimer's but remember that each patient is different. They will lose an ability at different times. My Mom lost her Auditory Perception very early in the disease. Others I have know did not lose this ability until very late in the disease. Mom also lost her ability to speak very early. Yet she walked long after both her Auditory Perception and ability to speak were gone. But I did notice that her walking went away when her ability to feed herself went away. Obviously her motor muscle control was begin affected by the disease. The brain in no longer telling her muscles what they should do. I also noticed a decline in her awareness of her surroundings. You have to look at Grandma's cognitive abilities and physical condition as a whole to determine where she is. Is she still responsive? Does she connect when you interact with her. Is she able to feed herself still? How is her physical health? It is all interconnected and no two patients are the same.
Tomorrow morning try to speak of something delightful related to Grandma. Did she make you smile? Did she say something that was humorous? Is there a memory that connects to the day that bring positive light?
Hope to hear from you soon and often