What happens to my data if I cancel my iCloud Storage subscription

My partner has additional icloud storage that my apple account pays for as she's added as family.

I now need additional storage for my data and see that if I take out a data plan she can use my plan if added as family.

If I remove her as family how long does she have before her additional data is deleted and if I then start an additional plan and add her back as family will her additional data then be added to my plan without her needing to copy the data.