Listing Mirror has the capability to "hide" an inventory source from your Inventory Tab on the Manage Listings page. This is a feature that functions on a per-user basis. So if user1 disabled inventory source A, user2 would still be be able to see inventory source A.
Here is how to set this up.
Select Show Inventory Sources from the Inventory drop-down menu at the top of the page.
Click on the Name of the inventory source that you want to hide.
Enable Make Hidden at the bottom of this page and then click Update Inventory Source to save changes made on this page.
And that's it!
For the user who disabled FBA 1, they will no longer see FBA 1 in the Inventory Tab on the Manage Listings page.