It made sense when I realized her son was basically becoming like serial killer. He fit the profile. He was a loner, he tortured insects and killed a cat, his dead twin was his imaginary friend, his only parent ignored him or was abusive. He was mean to his mother before during and after her necessary facial reconstruction surgery.

I suspected Lukas was somehow responsible for an accident that cause her to get heavy cosmetic surgery.
The Mother got the surgery because she wanted to, not because she had an accident or anything of the sort.
She went through a divorce, then the death of a son, so she wanted a "fresh" start.
Fine, fine, I'll leave! But first I'm going to bother these peanuts! Hmm? Yes? Hmm? HMM?