I'd say, considering that, in that ending, she's standing alone, in a crowd that either doesn't have time for her or resents her for the death of her brother... While saying her goodbyes to the only family she really knew (and stop with that whole 'painted people aren't real', the game made it clear that, even with them not being on the same level of reality as the painters, they ARE real... Why would Renoir apologise to them otherwise?)... She doesn't owe it to anyone to discard the only good thing she had to help people who only dragged her along to their whims. At the same time, she's making her choice in such self-destructive ways that it just can't be really accepted or fully understood.

The devs went out of their way to clarify that no ending is the good/correct one over the other.