Any ideas?

How about a set of loom bands? I've just ordered some for my grandaughter (age 8), but I hear that they are all the rage for older children too. Glad to hear that you GD is getting better.

Adult colouring book? Card making kit? Audio books? Jigsaws?

It’s not cheap, but Turing Tumble is fabulous: www.turingtumble.com/. I’ve spent some time with kids playing with it, and they were totally absorbed.

She’s just the right age for it. It’s physically undemanding but will interest and challenge her, and a side-benefit is that it will help her maths and IT skills.

If she is into reading,David Walliams books are so funny.
My gs`s favourite is Gangsta Grandma,and you might get one in a charity shop.
Hope she gets better soon.

Try the Happy Puzzle company. They have lots of good things. Ours particularly enjoy the Genius Square which can be played against other people or on one's own.

Good to hear your GD is getting better. I always go on Amazon and type in 'presents for 8 year old girls' (or whatever I am looking for in the way of presents). Up pop pages of good ideas and when you have chosen you can tell Amazon to deliver it direct to your GD.

Is she a 'gamer' Does she have ab Xbox? If that's a yes, they always welcome a new game. That's unless they're like my 2 who have them anyway.

Good to hear about your granddaughter. Make a camping trip nearby you. Hope this might help her to reduce boringness.