Re: Is it fixable? Wedding outfit...
You could either sew the top of the shirt, double it up (the seam where the shoulder blades are) and make make the neckine smaller, however this can mess with the rest of the fititng of the shirt.
Use double sided tape and stick the kameez just above your cleavage line.
Drape the dupatta in a way that cover the neckline (bad idea though if the kameez is heavily embroided)
Find a top to wear under thae kameez, which is the exact same colour. (might make you look bulky though if kameez is very tight fitted.
Congrats and good luck, post pics soon so we can see.