It is you who decides on how much access your collaborator has to your Storage.
On this Sidebar > Account > Collaborators, you get the option to change permissions for each collaborator by pressing the “Change Permission” button on the right side of each collaborator.
By checking and unchecking the boxes about Storage, you're authorizing your collaborator to have control over your files and decide if you will allow your collaborator to Create a Storage Folder
Update Storage Folder or Delete Storage Folder