Maxium font size

[Upcountrygirl]

Hi, I need an answer to a simple (?) question.
My mother has poor eyesight but loves reading ebooks on her Kobo Aura 2. However, as her sight gets worse we are hitting the limit of the largest possible font size. (She needs it really big. If I print something for her, I use 50 pt.) I know that settings vary from book to book and from publisher to publisher, but... this is my question:
For a given book, if we buy a bigger e-reader, will we get a bigger maximum font size? Or will we just get a bigger page containing more words the same size?
Do any e-readers have super-large settings that help people with this problem?
Any advice would be greatly appreciated. Don't tell me to get audio books, unfortunately they send her to sleep.

[Ika Apo]

What I for sure is that you should definitely not get a kindle. I also have poor eyesight and struggle with most books as kindle doesn't allow me to maximize the font size.