My niece went through a phase last year where all she wanted was princess stories, so I had to become a bit of an expert on where to dig them up without spending a fortune. The public library's OverDrive or Libby app was the absolute MVP – you just need a library card, and you can borrow ebooks and sometimes even audiobooks of classic princess tales. The selection is usually pretty solid for traditional stuff.
Beyond that, I stumbled onto a few digital libraries like Project Gutenberg. They've got all the old fairy tales and early 20th-century princess books that are in the public domain. The language can feel a bit old-fashioned for a modern kid, but that's part of the charm sometimes. I also noticed some newer indie authors post short stories or first chapters on sites like Wattpad or Royal Road, using the princess archetype in fantasy or sci-fi settings, which can be a fun twist.