We know that how children turn out is a combination of a whole range of things including genetics, parenting and other environmental influences. Despite that think Lynda is totally right in blaming Lillian for James being a dick. He is a dick and Lillian just encourages him.
Lillian’s low blow was pretty bad but then she sort of sighed as if she regretted it chose to say something else awful like “run away then”
So I would have to say I am siding with Lynda on this one.