Best House Phone for an Elderly Deaf person

Trying to get phone for a 90 year old who has 3 difficulties
1) very deaf. She has hearing aids but it is still very difficult for her to hear.
2) She constantly forgets to click the off button on the phone. Instead she buts it back on the charger thinking that turns the phone off (like her old phone). So when we ring we cant get through to her.
3) The screen needs to be large and easy to read.
Any help appreciated