Gremaud, 18, underwent a CT scan and passed concussion protocols after falling and banging her head so hard in training that she appeared to suffer memory loss.
But she recovered to take silver behind fellow Swiss Sarah Hoefflin -- who also hurt herself in training. Britain's Isabel Atkin won bronze.
"I just know what they told me, (that) I was shocked and then we skied down. I was crying. I really don't know what happened," she said. "I forgot everything about yesterday's training until I got into the ambulance. I went to the hospital and got a CT scan and everything was all right."
Switzerland's team doctor German Clenin said Gremaud fell off a railing and hit her head, but was not unconscious. She passed concussion protocols despite having a slight headache on Saturday morning.
"I did neurological testing yesterday (and) this morning so I could give the 'go' this morning," he said. "It's really important to watch and be careful with concussion and if there was a concussion, she wouldn't compete today."
Hoefflin said she had also had a tough week after falling and hurting both heels as she struggled with windy conditions in training.
"It's been incredible. It was a pretty hard week for the whole Swiss team, especially for me. I didn't have the best training and Mathilde and I have been having a couple of injuries," Hoefflin said.
"We came out today and wanted to have the most amount of fun. We wanted to push ourselves and be a part of it. I am so honoured."