Add meeting attending recurring series and sent to all users?

We are using Exchange Online and Client on Outlook 2013 has repeated issues when adding recipient to a recurring meeting. Makes no other changes to the meeting, but a meeting invite is sent to ALL meeting attendees. She is not prompted to send to only newly added recipient.  Why not?   I found reference to http://support.microsoft.com/kb/2649499 but this is Exchange 2010 and not Exchange Online.  Any helpful advice on this one?

Thanks.