Gliffy Online gives administrators of multi-user accounts the ability to add and remove user access to specific folders in the account. To use, first set up folders following the directions here: https://www.gliffy.com/user-manual/?productId=3#article_23
Then, set permissions by clicking on Permissions from within the folder settings and a dialog box will appear.
On the left side it will list all users that have access to that folder. If you want to remove access from a user for that folder, click on their email in the Users WITH Access column and then click the button to move their email to the Users WITHOUT Access column. Click Done to save your changes.