If she abruptly cancels it I suspect you would receive a notification about your device no longer being able to add additional files to iCloud.
Read this article about downgrading: Downgrade or cancel your iCloud+ plan - Apple Support
It used to include items such as:
● If you leave a family that shares an iCloud+ plan and you're using more than 5GB of storage, you can buy your own plan [ Buy iCloud+ or upgrade your current storage plan - Apple Support ] to continue using iCloud storage.
but Apple for some reason decided to remove that bit.
Apple doesn't say what happens to current items. They do not mention a grace period, but then they also do not not mention a grace period. My understanding with Apple Music is you pretty much instantly lose your playlists etc. However, for iCloud files, if you delete one it is held in storage for 30 days should you wish to recover it. You aren't deleting one, but what I am am saying there may be various scenarios possible and you had best ask Apple about this. All the documentation says is once you downgrade you can no longer update or add files.They don't say anything about deleting them (but again they don't say anything about not deleting them; Apple is somewhat vague in its statements; they do not like saying anything negative sounding even when it would help a lot to simply be clear in their statements).
This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple Support - Apple Support For some countries look under “Other” listing at the end of each region. Not every country has telephone support.
