Gamora isn't surprised by his sudden mood swing even if she's confused as to what caused it. She knows what a wedding is obviously. The details of it though frankly elude her. Her parents never got the opportunity to take her to one before their deaths. Thanos was more the type to kill off the wedding party before the wedding could actually happen.

"No." She stares at him in open confusion. Surely the ceremony can't be that special, can it? "Why should I be?"