YA book with girl riding a white owl (blue cover, read in Spanish around 2013).

Hi! I'm trying to identify a book I read years ago. I only remember the cover and a few details:

The cover was mostly blue/purple, showing a dark-haired girl riding a big white owl (or very close to it).

I think the protagonist's name was Raquel or Rachel.

I might remember a brother being involved in the story, but I'm not 100% sure.

I read it in Spanish around 2013, though it could have been an older book or a translation.

It was definitely YA/juvenile fantasy.

Unfortunately, I don't remember anything else.

Does anyone recognize this book or its title? Thank you so much in advance!