That's a very common and frustrating situation. The reason your photos are still on the iPad is that even though you logged out of your iCloud account, the photos that were synced to the device remained as local copies. iCloud Photos is a synchronization service, not just a storage service, so when you logged in, it downloaded and synced your entire library to the iPad.
To safely remove them without affecting your own iCloud account, you need to follow these steps carefully:
Step 1: Confirm You Are Logged Out
First, double-check that your mother's iPad is completely logged out of your iCloud account.
- Go to Settings.
- At the top of the menu, it should say "Sign in to your iPad." If it shows an Apple ID, you need to tap on it and sign out. This is a crucial first step.
Step 2: Delete the Photos from the iPad
Since the photos are now local copies and the device is not connected to your iCloud account, you can safely delete them directly from the Photos app on the iPad.
- Open the Photos app.
- Tap Select in the top-right corner.
- Tap Select All to choose all 54,000 photos.
- Tap the trash can icon to delete them. You may be asked to confirm.
This process will likely take a while due to the sheer number of photos. Once deleted, they will move to the "Recently Deleted" album. You should then go into that album and select "Delete All" to completely remove them from the device.
Important Note:
As long as you are logged out of your iCloud account on that iPad, deleting the photos from the device will not delete them from your personal iCloud account or any other device linked to your account.
[Edited by Moderator]