It all comes down to OBedience. SIT means sit until released.
How much 'off-season' training (frequency) do you do with her?
Are you hunting from a boat ? blind on land ? blind in water ?
Until then, you need to be using a tie down to prevent her from breaking. Dogs get sloppy in hunting situations (as compared to training) due to the added excitement. Another thing to do is take a hunting partner with you and let the partner do ALL of the shooting and you can concentrate purely on the dog (and have ecollar in hand).
When you're training, what are you using as retrieve objects - bumpers - frozen birds - live birds or what? What are you using as a "gun" in training?