When running reports in Audit Trail, you may be able to distinguish between the multiple users using that one account by also looking at the "Host Name" column; this would apply if the users sharing that account are logging in from different computers. Audit Trail will show the user name that logged in, along with the computer name (Host Name) they logged in from, and the Application they used when logging in (i.e. LF Client, WF Designer, etc.).

This also applies when viewing the active sessions in the repository, within the LF Admin Console under "Activity > Sessions"; this will show the users that are currently logged in, along with the same information above (user name, computer name, and application).