@.access:
I think the point is that O-Lin is her self as it would have been if not spoiled and tainted by her life story. Linlin is what was made of that person.
The core of Linlin is the generosity shown by O-Lin and Totto Land is in theory the proof of that: a utopia where everyone can live as equal (her dream being literally everyone sharing food on a table standing at the same height and meeting eye to eye couldn't be more clear). Linlin had her nature distorted by her growth, but her personality is rooted on O-Lin.
I agree with this. O-Lin is a chance for READERS to understand Big Mom better, not to "change" Big Mom for the better. O-Lin is not fundamentally different from Big Mom, and Tottoland is the best proof of that as a place where food is literally free and shared by all.