IMO, NemosMum has some excellent advice. And obviously, she knows more than me. I just want to add, once again, that, in the end, only the parents can make these decisions, not a granny (unless she has custody/guardianship). So you can relay this advice to the parents, Margsus, but then it's up to them. I hope they make the right choices for their child.
I'm also wondering if the adults in GD's life talk to her very much. Since her understanding is good, they probably do. But if they/you don't, maybe it's time to start. And I don't just mean the obvious comments, which, clearly, are already being made. I remember reading, when I was a young mom, that it's good to talk to babies about anything and everything, even stating the obvious ("I'm changing your diaper now," "Look! Here's your bottle!" "Ooo! Hee, hee, hee! I'm tickling your tummy!" - all while making sure she sees your lips moving. That may help and it's something you can do when you're around, if you haven't been doing it already.
Best of luck!