The website is very clear on this - http://www.skyteam.com/en/Why-SkyTeam/SkyTeam-Lounges/

"In addition, SkyTeam Elite Plus members are allowed to invite a guest, who is also traveling on a flight operated by a SkyTeam member airline, to join them in the lounge. The guest does not necessarily need to travel on the same flight as the SkyTeam Elite Plus member."

Same situation on Star Alliance - http://www.staralliance.com/en/benef...silver-status/

"Airport Lounge Access - available worldwide for you and a friend1 when you travel with any Star Alliance member airline, regardless of your class of travel."

As is oneworld - http://www.oneworld.com/ffp/lounge-access/

Why do you expect them to make an exception in your case? If not, why not in every case? And if they make the exception in every case, why have the policy at all?