She can access her iCloud information the same way she would if she wasn't sharing your storage plan.
For synced data such as iCloud Photos, she can use any internet browser and log into icloud.com. What you can access via a browser varies by device. See the information in the following Apple article: Which iCloud.com features are available in the browser on your device - Apple Support
Synced data will also automatically sync to a new device when the same syncing option is turned on in that device. Also see: Set up and use iCloud Photos - Apple Support
Also note that while she can view synced data as described above, it is not possible to view the contents of an iCloud Backup of an iOS device. She can only use the backup to do a full restore of a device or to setup a new device. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Apple also has an article about managing iCloud storage. See: Manage your iCloud storage - Apple Support