That’s not a writers beware. Work-for-hire isn’t hidden in a contract somewhere. It’s a COMPLETELY different contract, and she knew exactly what she was signing.
Work-for-hire is actually a very lucrative (and fairly common) way for experienced writers to have a steady income. Does it SUCK mightily to have the book become popular and you don’t share in the proceeds? Yep. But that’s how it works. It’s not your property – it’s a writing assignment for a company.