Sounds dreamy!!!
No one should be studying for their GCSEs in the summer holidays! What?!
Reading for pleasure is so good for her brain, understanding of the world and her emotional development. You'll be doing her a huge favour by supporting her ambition to read through the summer weeks.
Especially because it's the ultimate transportable activity. She can read in the garden, in any number of local parks, at local beaches.
Good for her. Literally good for her!
I'm a big reader and always have been. I've now got an excel spreadsheet with a worksheet for each year's reading list and accompanying TBR list. I have a worksheet for the BBC 100 books to read before you die and a couple of other reading lists that I also update when I read something off the list. I've got a worksheet of 30 different genres/types of books to read through the year that helps me to mix things up and not get stuck in a genre hole. This includes "a book written 100 years ago", "classic horror", "about a culture you're unfamiliar with", "an author the same age as you" etc. I also use the Goodreads Challenge to mix up my genres, get introduced to new authors and all sorts. So good to hear she's got her own version of the 100 TBR!
For those who've inferred that reading lots = not socialising, that's not true for me! I'm going to a big gig with friends on Friday and I'll read on the train on the way to meet them. On my summer holidays away in the sun with friends as a teenager we'd all be reading on the beach or by the pool and still manage to flirt with boys, drink fishbowls and have fun. It's not one or the other.
15 is a really hard age to get a job these days as lots of places won't take them that young but if she's able to do some babysitting for family friends, that could help her save up some pennies over the summer. (She can also read once the kids are in bed!)
In the summer pre GCSEs and pre A Levels and pre English Lit at Uni I included the titles of books I knew we'd be studying through the year alongside books I'd chosen for fun. I loved Jane Eyre and Sylvia Plath more for having explored them on my own in gardens and beaches and parks before then trawling through them with a fine tooth comb in school.
Not sure whereabouts you're based but there are some fab bookish days out that she could do with you or friends to enhance her reading challenge. Within a day-trip drive or train from me this would include Hay-on-Wye with all its many many many bookshops, some antiquarian, some second hand but all fascinating; and Bath for the Jane Austen Centre. Or go to the cinema with mates after reading a book that's been made into a recent film. (Animal Farm is out in late July but there are loads on Netflix etc too).