What to do when Mom forgets her routine?

When is the last time she had a good eye exam? She may need reading glasses to see the knitting.

Since she has dementia, I wouldn't expect her to remember a routine or how to do a lot of things. It's typical of dementia that things are forgotten over time. Of course, you can review things with her doctor and have it checked out. Most do blood work on a regular basis to make sure their physical health is okay. If she is unusually confused, I would report any change in mental status to her doctor.

Does your mom live with you? In most Memory Care facilities, the staff go to the residents rooms and announce the upcoming activity is about to start. They wheel those who need help into the room where they gather. They gather those that enjoy the activities into one place and have their music session, exercises, movie time, etc. If they didn't do that, the residents would not likely remember it themselves. They also do this with meals and snack times.

If she's too tired or not interested, I'd accept that. The dementia will gradually cause them to be unable to participate in most activities.

My cousin still seems interested in things, it's just that she looses focus in just a minute or two. I think that is quite common.