Call Her on the phone and talk to her. As a Grandma when I offer something to my kids or GKs, if they don't want it and I don't want it, I'll think of someone else who just might want it.
Get on that phone right now. Don't email her, make a personal phone call!! Show her you ARE indeed interested in it, and confess to her you were worried at her paying all that money for it and not getting any good out of it. BUT you do want it. desire it, are in raptures at the very idea.
TALK TO GRANNY RIGHT NOW. SHE JUST MIGHT BE ON THE PHONE OR EMAIL TO SOMEONE ELSE, ASKING IF THEY WANT IT.