Just thinking of the books I loved as a child:
The Drina ballet books - about a girl whose mother was (unbeknown to her) a famous ballerina who died tragically. The books are about Drina’s longing to dance against the wishes of her grandmother and how she secretly has lessons.
The Lioness books by Tamora Pierce. She’s written lots of books set in the same world and I loved them all, but the Lioness ones were where I started. They are about a girl who pretends to be a boy so she can become a knight, there are wizards and magic spells too. I loved them.
The Carpet People and other Terry Pratchetts for younger readers.
James Herriott - loved
his vet books.
Joyce Stranger - lots of books about animals. Sheepdogs, guide dogs, horses, foxes, police dogs. Loved them all.
The ponies for Jill books - v horsey and jolly but great fantasy fodder if she’s into ponies. Or Jackie Jumps to the Top - about a girl who buys her favourite riding school pony at auction and keeps her on her dad’s garage plot (handy!) and ends up showjumping for Britain, natch. Or Afraid to Ride - about a girl who regained her riding mojo through a special ’unrideable’ pony (in real life we’d be talking A&E here but suspend the disbelief...)
Enid Blyton? Loved the Famous Five and Mallory Towers books.
The Hobbit?
Thunderhead and The Green Grass of Wyoming books - about a boy on a ranch and the special colt he loves, which ends up being a wild stallion in the mountains.
Redwall - about anthropomorphic mice and another animals who live in an abbey and are beset by evil pirate rats and foxes. Loved them too.
I had so many of my Mum’s old books so loads of these are probably out of print! But you could find them on eBay, I bet.