I'd bet $ that she's intimidated by the size of the birds. Even Syrus on occasion will struggle to pick one up and needs a "Bring it!" from me to get him pumped enough to just grab what he can and come running with it.
Take one of your dead geese and train her with it, teach her how to grab it where the neck joins the body (on the body though, not the neck). It'll take a bit but she'll get it. Work from just having her sit and hold the goose in her mouth, to doing short (5') retreives, to doing longer and longer retrieves with it as she gets more comfortable. Get her all fired up too and maybe mix in retrieving the goose with retrieving her favorite bumper or toy so she gets the idea. Most of all, just be patient.
Swatted 2 more geese last night, should've had a lot more but had an inexperienced buddy call the shot too soon. Knocked one down and it hit the water swimming (we were in a swamp) and Syrus took out after it. They disappeared behind a brush pile about 50 yards out with Sy swimming about 10 yards behind the goose. I was getting a bit anxious as several minutes later there was no sign of either and I was just getting ready to whistle Syrus back when I could see ripples in the water. Here came Syrus with the goose in his mouth! haha I love that dog!
"Knowing when to shoot and when to wait is one sign of maturity in a bowhunter. Be patient and pick your aim point carefully." ~ Randy Ulmer
"I suppose it's the way of hunters. We are very odd fellows." ~ Peter Hathaway Capstick