Pluck a duck them go pluck a pheasant. Upland birds dust their feathers and waterfowl oils them. What is easier in to hold in your own mouth? Warm Bread with butter or a saltine cracker? Same is true for dogs. Then after the hunt go find Bubba an pals for a 30 pack of Coors light to make sure you don't catch a cold
It's new to her, she'll get better. Give her lots of encouragement when she's holding a bird, and as mentioned already, keep out a bird or two to practice with. It takes some time for a dog to learn that pheasants are harder to hold than ducks, and there are better ways to pick them up than just grabbing the first part they get to. Our dogs have learned over time to pounce on the cripples and hold them down... then they take a moment to decide where to pick the bird up so they will have an easier time retrieving. If they have to, they'll snatch them first, then stand on them to get a better grip: it's just something they seem to learn on their own.