"“There is nothing more pathetic,” said Ciri sternly, “than a sorceress in tears. You taught me that. But now you’re pathetic Yennefer. You and your magic, which is useless.”
" Triss was surprised that the black-haired sorceress was able to withstand for so long."
"Then she ceased to be surprised because Yennefer stopped in the middle of the magic formula and fell on the pavement next to the witcher."
“I,” Ciri said slowly, still kneeling on the bloody ground, “I once gave up my power. If I didn’t, I could save him now. (notice the lack of Yennefer needing saving) I could cure him. I know it. But it is too late, I can’t do anything. It is like I killed him myself.”
"The silence was broken by Kelpie’s whinny. Then by Dandelion’s muffled gasp. They were all stunned."
Dandelion gasped, this time in awe. Triss felt overwhelmed by her emotions. Euphoria. "
“Ihuarraquax,” Ciri spoke to him. “I was hoping you’d come.”
"With one hand she touched the unicorn’s horn, with the other she touched the witcher. From her fingers drifted a ribbon of flickering light."
Ciri is reviving Geralt through Ihuarraquax, who is a unicorn. Unicorns (in mythology) have the power to heal people, through their horn. Ciri is the necessary vessel because (notice how Ihuarraquax strides in over water without actually walking on it, and the book mentions Dandelion and Triss's shock at how it came to them, despite knowing the legend of unicorns running 'light, agile and silently'), he is most likely not 'in their world', but Ciri has the ability to bridge them.
Now the part with Galahad, does suggest they never were married, and Ciri tells Triss she doesn't know what she's asking, but we can be certain Yennefer and Geralt are alive...they may simply be unable to come back to the 'witcher world', due to Ihuarraquax's magic healing. If his magic would have worked in the witcher-world, he'd just have shown up entirely in their world, instead of as an apparition.