Did you try to stop the sharing?
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Add or remove subscribers, or turn notifications on or off
Select the shared album, tap , then do any of the following:
- Add subscribers: Tap Invite People, then enter the names of the subscribers you want to add.
- Subscribers can add photos and videos to the album. Turn off the Subscribers Can Post button so only you can add photos and videos.
- Remove subscribers: Tap the name of the subscriber, then tap Remove Subscriber.
- Turn notifications off: Tap the Notifications button. Tap again to turn Notifications on.
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copied from: Share iPhone photos with Shared Albums in iCloud - Apple Support