Originally Posted by
andset1191
I think people are missing the point here.
A oneworld emerald was flying Malev, a oneworld carrier. Thus he/she is entitled to use the "First class lounge" that that carrier uses at that airport.
At Amsterdam, Malev use the KL Crown Lounge, therefore, the holder of the BA Gold Card is entitled to access this lounge with one guest.
oneworld benefits exist for a reason; sadly most carriers apparently ignore this fact.
The flight must be operated and marketed by a OW carrier. I am not sure what was the case with the OP but if the flight was booked under KL code, it does not matter if it was operated by MA.