At the minimum, get a 4K TV, at any size display. Must have 4k.
Samsung, Sony, LG, Panasonic, Toshiba, Philips. Maybe JVC. Some say Vizio, but I dunno.
I have a mostly uninformed belief that you really can't go wrong by just getting the biggest Samsung that you can afford. Just remember that you have to eventually move it too.
Modern TVs have streaming options built right in, if she is a Netflixer or Youtuber, or you can buy a
Chromecast and cast anything from the Internet to the TV.