Hi JeffreyCS,
iCloud Shared Photo Library works by moving photos from your respective personal libraries to the shared photo library that was set up. As such the photos that were migrated from before the feature was turned back off will not 'disappear' back to her library, they're a part of that shared library now.
"How iCloud Shared Photo Library works
When you contribute photos and videos to iCloud Shared Photo Library, they move out of your Personal Library and into the Shared Library. You can join one Shared Library, and you can choose what to share, or automatically share content straight from the camera. All participants have equal permissions to add, edit, and delete content in the Shared Library, while the person who set up the Shared Library, the library creator, provides iCloud storage for all of the content. Everyone else gets access to the Shared Library content without it counting towards their iCloud storage.
When you join a Shared Library, iCloud captures a one-time snapshot of your photo library database and associated metadata and stores it for up to six months. This helps with a smooth transition of your content to Shared Photo Library. Any photos that were in your library at the time of the snapshot that are subsequently deleted are also stored in iCloud for up to six months. "
Best recommendation if you do not want to use that feature is to import those photos from the shared library back into the respective owners libraries.
Cheers!
