When joining your family sharing group did she accept the offer also to join your (shared) iCloud+ space?
If not she can do this at any time. Apple has instruction for this in the section of Share iCloud+ with your family - Apple Support called Switch from your personal iCloud+ plan to your family plan. Using her device follow these instructions:
On your iPhone, iPad, or iPod touch
In iOS 16 or iPadOS 16 later:
- Go to Settings > Family.
- Tap Subscriptions.
- Tap iCloud+.
- Tap Use Family Storage.
In iOS 15 or iPadOS 15 or earlier:
- Go to Settings > [your name].
- Tap Family Sharing, then tap iCloud+.
- Tap Use Family Storage.
On your Mac
In macOS Ventura or later:
- Choose Apple menu > System Settings, then click Family.
- Click Subscriptions, then choose iCloud+.
- Click Use Shared Plan.
In macOS Monterey or earlier:
- Choose Apple menu > System Preferences, then click Family Sharing.
- Click iCloud Storage.
- Click Use Family Storage.