I've always found the right interpretation to be the best one. You don't get any closure with your interpretation that a unicorn comes and heals Geralt. The correct interpretation is the one that brings all the themes of the books to a poignant close. Geralt learns that neutrality is untenable and that he is no longer the witcher he thought he was. Yennefer swallows her pride and makes an ultimate sacrifice. And Ciri learns in the end that eschewing responsibility has a cost. In any case, there is no even implication that Geralt and Yennefer are alive until the seen when the wake and it certainly doesn't occur to Triss or any other onlookers that this is the case.