Where does she live? In the US, many states have Senior Centers that provide activities and stimulation for older adults, and there are some Adult Day Care centers specifically for people with disabilities and/or dementia. Most states also have nonprofits that serve people who are blind; they provide services including a device that will play audiobooks. If she is in the US, I highly recommend contacting her primary care provider‘s office, who can probably get you started with the local resources.

The dementia is the harder thing to deal with here. Could you get an alexa for her at least?

What level is her vision? What were her previous hobbies? And how bad is her dementia?

If the dementia and memory loss is really bad, it's harder to learn new skills, so leveraging known skills can be useful. It also makes things like planning ahead and keeping track of what is happening difficulty as well. While some people like listening to the radio or TV with descriptive video, it's pretty passive.

I know one lady who used to know how to knit, and my coworker was able to teach her enough she could knit blind. Because of minor memory issues, ehe couldn't make complex things, but she was able to makes dishtowels and other simple objects such as scarves.