The question raised in social media:
1. Why Prime Minister of Malaysia bring his wife?
Because the invitation mentioning both, head of the state and wife. The invitation clearly mentioning both and there is not an issue for DS Rosmah Mansur to attend the ceremony.
2. Why DS Rosmah walking in front DS Najib?
It's all about seating arrangement provided and arranged by the host. In this case the organizer has allocated DS Rosmah to sit on the right hand side of DS Najib. Therefore, Datin Seri get in first. Each event has customs and protocol. Unlike going to the movies. You and your wife might exchange seats without any restrictions or protocol.
Among leaders of the countries invited together with their wife were, wife of the vice President of Indonesia, wife of Prime Minister of Vietnam, wife of New Zealand Prime Minister and wife of Prime Minister of Singapore.