Gina had no intention of wearing a wedding dress to Jake and Amy’s wedding.
Gina bought Amy a backup wedding dress just in case.
Observe: the dress Gina gave Amy is 100% not Gina’s style. Gina doesn’t do lace; she’s not into a delicate or classy look; Gina goes for stylish glam in episodes where she dresses up. But Amy? Whose pre-Jake apartment was covered in doilies? Amy goes for that style.
In the Boyle Linetti Wedding episode, Gina had a gorgeous dress ready for Amy when Amy arrived filthy from catching a perp. Gina claimed it was “in case I hated your outfit.” Yet the dress looked perfect on Amy; it wasn’t something embarrassing…
So, when Amy and Jake get engaged, Gina buys a back up dress. Amy just tore up a wedding dress chasing a perp she saw while she was in a bridal store; there’s a solid chance something will go wrong on the day of the wedding, and Gina Linetti is gonna be prepared for when those dumb dumbs get filthy.
Gina Linetti wasn’t gonna wear that dress to the wedding. She just didn’t want to admit that she did something so thoughtful and nice for Amy.