I don't begrudge your opinion; if any champion deserves an immediate rematch, it's probably Valentina. But personally, I don't believe in immediate rematches, especially where the champion got finished. I don't care if she/he had 20 title defenses; if they lose the belt and get finished, they should have to win at least won fight before getting a rematch. Immediate rematches hold up divisions and leave deserving contenders twisting in the wind.
From the UFC's perspective, I understand immediate rematches in cases like Usman-Edwards. There's money to be made on the rematch, and they don't want to risk it by letting Edwards get beat by someone else. But that doesn't apply here: a Valentina-Grasso rematch doesn't make much sense from a monetary perspective. And it doesn't necessarily move the needle from a fan perspective. For the most part, I think the only people who truly are about an immediate rematch are Valentina and her fanbase.