I'm not going to quote all you've said about Scarlett's mom. I feel that most of you caught a good part of it.
Well done Xapican, that is exactly what I was waiting for you guys to get to.
She has a Narcissistic personality. All that she cares about is herself. Even the fucking rapist boyfriend, she doesn't really care much about while he satisfies her. He can lie, rape hurt whoever he wants, as long as she gets satisfaction from him. Scarlett, only mattered as a means to extort money from Edmund. She never worked, she made him sustain her and Scarlett, I imagine the blackmail he was under. Not that he didn't deserve it.
I may be a bit too close to the subject, my first wife managed to block me from my eldest daughter life, to the point that we are now complete strangers and my daughter has nothing but hate for me and her (half)siblings. So, maybe by opinions are tarnished and shouldn't count here.
TBH, she doesn't deserve even a hate fuck. I hope her rapist boyfriend provides her with has much hurt and pain as she deserves for what she inflicted on Scarlett for 18 years. Fuck her? No. HELL NO. I'm way more inclined to some more drastic means, that would get me banned if I say them.
Someone mentioned she being deaf as an excuse for her behavior. Sorry, no. She was already deaf when she started an ilicit relationship with Edmund that was already married and had 2 kids. Yet, being a narcissist she cared only for her own pleasure and went with it, her parents probably saw it has an opportunity to get rid of her.
Now, it's the MC's turn to give our dear Scarlett what she had only received from Daphne. Love and care. I hope he spoils her rotten. She'll need it. But her learned behaviors that she inherited from her mother will be with her for all her life.
Peace