My daughter deleted all the pictures off her iPad and now they've disappeared off of all her devices.
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Step One: The first thing to do is go to iCloud.com and log into her specific appleID. From there you can look at any pictures that are stored in the cloud and therefore retrievable. If they are in the cloud then you can move to step two. If they are not, that means they’ve been deleted from the Photos app and the deletion will have synced across all other devices as well. Photos acts just as your email would. If you delete pics in one place, they are removed everywhere else also. But if they have been deleted then next look in the “recently deleted” folder. Apple’s Photos app keeps copies of all deleted pictures for 30-40 days before they are permanently removed.

Step Two: check that you’re logged into iCloud on each device then under iCloud settings on the phone and computer (in system preferences) select the photos area and make sure Photos is turned on.