Did she have one spook her before?
My old yellow lab Bear went after one that was wing shot and not quite finished. It stood up and hissed at him. Scared the bejezuz out of him and he wouldn't retrieve for a while after. Just circled and circled. After a bit he figured it out, but that was his deal.
We tried tying a wing down on his retrieval toy, thinking that maybe we had to start over with him, but he was too smart.