What is Yennefer thinking about?

Question

At the end of Blood of Elves, Yennefer and Ciri have the following exchange (emphasis mine):

“Lady Yennefer?”

“Yes.”

“What are you looking at like that?”

“At that tree. That linden tree.”

“And what’s so interesting about it?”

“Nothing. I’m simply feasting my eyes on it. I’m happy that . . . I can see it.”

“I don’t understand.”

“Good.”

Silence. No words. Humid.

What is the meaning of Yennefer's words? Is she remembering some fond memory with Geralt?

Please avoid spoilers of future books in your answers.

Answer 1

Valorum's comment is correct: Yennefer did indeed lost her sight, as we are told by Triss in Blood of Elves, chapter three:

Damn it, I’m Triss Merigold, the Fourteenth One Killed at Sodden. There are fourteen graves at the foot of the obelisk on the Hill, but only thirteen bodies. You’re amazed such a mistake could have been made? Most of the corpses were in hard-to-recognise pieces—no one identified them. The living were hard to account for, too. Of those who had known me well, Yennefer was the only one to survive, and Yennefer was blind. Others knew me fleetingly and always recognised me by my beautiful hair. And I, damn it, didn’t have it any more!
_{Emphasis mine, translation by David French}

Battle of Sodden happened during the "Something More" short story, which, I believe, finishes the Sword of Destiny anthology.