The streaming device she wants to get is the Amazon Fire TV stick, because it has a memory chip in it that buffers streaming NetFlix, AmazonPrime (that Roku doesn't have) and more, and costs $40. She has a lot of DVDs that she enjoys, so the player makes sense for now.
She has televisions in other rooms and is planning to use them on antenna and to move around a streaming device to those rooms (after the dish devices are all removed), so depending on what all she decides she wants to stream, the stick or Roku would equally be good possibilities. My sister has a Roku and likes it a lot. On the down side, the fire stick has a small remote - easily lost (though it also has a phone app that can substitute for the remote). What about the Roku? How large is that remote?