Sue needs to make more room on her iPad. Leo says to turn on iCloud photos, and select 'optimize iPad storage.' Not download and keep originals. Then it will backup the full resolution versions in iCloud and replace them with lower resolution versions to make room.
Leo would recommend backing up through iTunes first. Another option is to use Google Photos and Amazon Cloud Prime to backup her photos. Then she'll have three different backups just in case. She can check out details at 9to5mac.com.