It was very rarely that even the queen or the royal children were allowed to sit at the king's table, which is probably the reason why Nehemiah mentions the fact that the queen was sitting by him.

Perhaps he hailed the circumstance as a proof that the king was in good humour that day, and would therefore be more likely to listen to his petition.

But no one who was not closely related to the king was allowed to sit at the royal table, even the most privileged courtiers sat on the floor and ate at his feet.
The feast has begun, and it is time for the Rab-shakeh to present the wine to the king.

He takes the jewelled cup from the table in the king's presence, he carefully washes it, then he fills it with a specially rare wine, named the wine of Helbon, which was kept only for the king's use.
This wine was made from a very fine growth of grapes, at a place in the Lebanon not far from Damascus, named Helbon.

Then Nehemiah pours a little wine into his left hand and drinks it, and then, lightly holding the cup between the tips of his fingers and thumbs, he gracefully presents it to the great monarch.
Artaxerxes glances at his cup-bearer as he rises from his knees, and at once notices something remarkable in his face.