If your grandmother has never owned a parrot before, I would highly advise against a macaw as a first time bird. They are one of the most advanced parrots to keep.
They need an extremely large cage, a lot of attention, enrichment and care. They also run anywhere from $1k-18k depending on the type of macaw. They can also be aggressive, and can bite extremely hard (hard enough to remove fingers and flesh).
I would recommend starting out with a cockatiel or a parakeet, so you know what you're getting into with a smaller parrot first. I hope this helps!