This is Nat, motherfucking deal with it. JK no doges. Probably.

She is covertly scanning the crowd for any suspect behavior and if you have the wherewithal to catch her talking to herself she's actually reporting back to Nick, something she'll quickly cover over. Other than that, she's perfectly agreeable, congratulating the beautiful couple. Putting her gifts for Tony and the engagement at the table. What? Word gets around S.H.I.E.L.D. fast.