Skype For Business - Showing Out of Office For User Who Is Not OOF

In my Exchange 2016/SFB 2015 environment, I have a user named Mary, where OOF is showing enabled/turned on when looking her up in SFB and Outlook:

The problem is: she isn't Out Of Office, she's there, sitting at her desk.

In the Exchange Management Shell (and the ECP in "manage another user") automatic reply status shows as disabled:

Well, we know the EMS doesn't lie, so it's gotta be client-related.

We tried turning off Outlook cached mode, creating a new local mail profile, and deleting Mary's SFB cache...nothing worked.

On a hunch, I checked Mary's calendar and one of her direct reports named Laura, sent her own OOF as an invite to Mary, which added it to Mary's calendar, therefore showing Mary as OOF:

That's bad practice, and totally confusing for other users. 

To fix it, Mary needs to delete Laura's calendar event and it will remove Mary from looking like she's Out Of Office.