I think Lisa genuinely likes Erika, while I think she secretly hated Denise despite their years of being "good friends" (didn't they share an ex or two in common? Lisa laughed it off but maybe there's some grudging feelings there). But she, Door-it, and Kyle are also probably scared of Erika as well.
Don't some of the allegations pre-date the accident? So Erika can't claim that Tom only did what he did because of a head injury. Or wait, was it the dementia? Or wait, did the dementia cause the accident? Yeah Erika, you blew it. No wonder you were crying/hyperventilating in the bathroom.