"Mom, you should calm down. Don't make impulsive decisions just because you're upset."
"Mom, you're overthinking it. Even without me stopping her, Joanna won't be with David."
Now that she's attached herself to someone as powerful as Mr. Parker, there's no way she'd be interested in David.
Her current goal isn't to stop Joanna from getting back with David, but to prevent her from being with Frank Parker.
If Joanna truly succeeds in seducing Frank and becomes his woman...
Then she would really ride above their heads in the future.
"Why?" Rose Liall looked puzzled, "How could that little bitch possibly refuse? She must be dying to marry into the Benington family."
"You're underestimating Joanna," Annie Lawrence sneered, "She's already hooked up with an even more powerful man. David is nothing to her now. Mom, do you know who that man is?"
"Who? Could there be someone more powerful than the Beningtons?"