I read it as Alicia already knowing what is going on in painted Alicia's mind and letting her go. She is affected, but she also knows it is for the best and is at peace with that, while Verso "fuck everyone the kid has to stop painting" Dessendre wants to convince her to live even as he's planning to betray everyone. And it doesn't matter if Alicia plays pretend or not, the lumiere people are still real.
The details are of course impossible to know for sure since the exact nature of painting magic isn't explained, but it seems that Renoir and others see them as unique beings, not just as simulations. He just wants his family back. If that means genociding a pocket dimension, then he's going to genocide that pocket dimension.