an iPhone would have been much easier for her to use. The text to speech interface is more refind and the gesture controls are currently much easier for elderly or mobility impaired folks to learn and use with IOS, than they are with Android. The latest version of Android is more accessible, than prior iterations of the OS, though, so not all is lost. If you can't switch phones, which I realize is probabily unrealistic, you should make certain her phone is running the latest possible version of Android, lollipop or bbetter, and install an app called TalkBack, wich will allow her to browse the web, and use the other features of the OS. You might also want to download the NLS Bard application for her, so she can access the free audio books available from the National Library Service for the Blind and Physically Handicapped. The Audible app is also accessible, as is TuneIn radio, for streaming other audio content, Twidere for Twitter, Voice Dream Reader for reading e-books and text files, Audio Game Hub, for audio gaming, Tap Tap See, to use the phone's camera for identifying common objects, lemons VS limes, coke VS Pepsi, etc. You can find even more information about Android accessibility, and hundreds of other accessible Android apps, over at the Inclusive Android site: https://www.inclusiveandroid.com/
I hope this helps your Mom get the most out of her phone.

Sighted person, but my mom is blind. She's also elderly. She used to be a walking phone book, but as she's aged, her memory has deteriorated. Not dementia or anything, just not what it used to be. She's also not very tech savvy and somewhat hard of hearing. So it was a challenge finding her a solution that allows her to call people without requiring her to understand much about technology. Someone got her a "Vocally 3" device, but managing the phonebook was cumbersome, recording names became increasingly frustrating as you added more ("this name sounds too similar to another recorded name"), and it eventually broke anyway.

I got her a pay-as-you-go cell phone (I only wanted WiFi capability, not actual cell service), and I got her a Google Voice number. I got her a Samsung phone, because it has a tactile button at the bottom, and that activates the "OK, Google" listener.

I found an app on the app store called "Voice Plus", and it allows someone with a Google Voice number to place a call through another phone. This is important, because she's used to her home phone and how it works.

So now, the Voice Plus app is configured so that she can use her Samsung phone to say, "OK, Google, call John Smith", then the Google Voice service calls her home number, and when she answers the call, it rings through to whatever number is stored in her contacts for John Smith.

Even that took her a couple weeks to get used to. But she seems to be doing well with it now. It's not 100%, but it's the best solution I've been able to find. I can edit and add contacts from my computer, so there's nothing cumbersome about that, and in the instances where it has trouble understanding her, I can look up the number in her contacts and put the call through myself, regardless of where I am, as long as I have internet access.