What happen to the excess photos when icloud storage is full?

Hi, I have 200gb plan and share it with my wife. She has 102gb and me 125gb. It says that my family not using the family storage because not enough space. I checked that she still keep 90gb of photos on the icloud and everything else. So, if she is not using the family storage, then how come she still has the 90gbs photos stored on the icloud? How is this works?