Did you share your storage as described in the excerpt below from Share iCloud+ with your family - Apple Support
To share iCloud+, you need iOS 11 or later, iPadOS, or macOS 10.13 High Sierra or later. For the best experience, make sure your family members' devices meet these requirements, too.
On your iPhone, iPad, or iPod touch
- If you haven't set up Family Sharing yet, set up Family Sharing.
- Go to Settings > [your name].
- Tap Family Sharing.
- Tap iCloud Storage.
- Follow the steps to share your existing plan.
- Use Messages to let any family members with an existing iCloud+ plan know that they can now switch to your shared iCloud+ plan.
And did she switch her storage as described in the excerpt below from Share iCloud+ with your family - Apple Support
If a family member is already paying for their own iCloud+ plan, they can choose to switch to your plan or keep their own and still remain part of the family. When they switch to the shared family plan, they get a refund for the remainder of their personal plan. They can't keep their current plan and use the shared family plan at the same time.
On your iPhone, iPad, or iPod touch
- Go to Settings > [your name].
- Tap Family Sharing, then tap iCloud Storage.
- Tap Use Family Storage.