Yes folks, it’s Christmas present research corner 
So I have an elderly aunt who it struck me might enjoy Netflix. She’s pretty good with her tablet but we don’t want to push it.
If someone paid her monthly Netflix fee, and someone else bought her a Chomecast dongle … could she just pick shows from the Netflix account on her tablet and it would rock up on the big old tv*?
I don’t have a personal comparative experience, but reviews suggest that the most seamless interface is Apple Airplay from an iPad or Macbook via Apple TV. This will throw almost anything that auntie pulls up on an iPad or Macbook onto her TV reliably at the touch of a button. You need an OS that’s recent enough to have Airplay; but 3rd generation Apple TV (now $60) works fine.
I realize that this may not be the ideal answer given what you have already, but it can be implemented fairly cheaply (iPad plus $60) if you can’t get what you have to play well together.
The Chromecast interface is pretty easy to use. I set one up for an elderly friend, and she is using it just fine. And she’s technically inept, can’t figure out her tablet for the life of her.
How big is the tablet? My mother has been very happy watching “TV” on her tablet (RTVE and Netflix), but it’s a 10". After one of my brothers made the mistake of hiding the RTVE icon he was this >< far from being banned from her house.
I would think the best thing would be a smart TV with Netflix already on it. Much more easy to hit the home button on the remote, then click on Netflix.
And I suppose you could try it with the dongle. If she can’t work it, then give it to someone else, get her the smart TV.
A Netflix sub + Chromecast is the cheapest method, and if she’s technical/comfortable enough with her tablet, she’ll be able to cast to the TV pretty easily.
I actually prefer to cast via my phone, despite having a smart TV with Netflix app available. I find the mobile UI to be faster, more reliable and polished. As an added bonus, if she likes the functionality, she’ll be able to cast much more than just Netflix, in the future.
And worst case (if she for some reason just hates it), you can easily sell or avoid getting burned much, on the relatively cheap Chromecast.
Yes.
Btw, what tablet does she own?
With Chromecast there is a little icon that appears on the device screen when you are using a compatible app like Netflix. Tap it to cast to the TV, tap again to uncast. It’s pretty painless. So yes, it should work as you’ve described. We prefer to Chromecast from the tablet rather than use the Netflix app on our smart TV because it is much easier to navigate Netflix through the tablet.
Speaking strictly for myself, the least annoying way to get Netflix to the TV is a Roku.