I don't know if there are deficiencies in my English translation, but in my copy Yennefer's name is not carved on the monument. Gerald fears that it is, and refuses to read the last name. However he asks Yurga what the last name is:
“Nothing... Yurga... you really remember all of the names inscribed on the monument?”
“I'll test your memory... The last. The fourteenth. What is it?”
“But you're a real skeptic. Don't you believe anything? You want to verify that I'm not lying? I told you that even children know the names. The last, you say? Yes, the last, it's Yol Grethen of Carreras. You know her, perhaps?”
However Triss Merigold's name is on the monument and she is later revealed to be alive. In Blood of Elves Gerald says to Triss:
'I studied your impressive tombstone with my own eyes. The obelisk in memory of your heroic death at the battle of Sodden. The news that it was a mistake only reached me recently. I can't understand how anyone could mistake anyone else for you, Triss.'
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!'
The impression I get is that she wasn't mistaken for someone else. She was so badly burned that she wasn't recognised and everyone assumed her body had been blown to bits.