IMO she's WORSE than a sociopath. She knows right from wrong but was WILLING TO DO WRONG because of the perceived reward. Her undying loyalty to PF. You know her kind, the sort who'd do anything for a friend.
But see, those times she drove up from Oklahoma, at his bidding, intending to kill Kelsey, she couldn't go through with it, but went so far as to show up at Kelsey's door. Where she saw with her own eyes that Kelsey was warm, polite and a mother.
Rodeo Queen couldn't bring herself to kill Kelsey... but we don't actually know that, do we? That coffee could well have been poisoned.... only Kelsey never drank it. If it was poisoned and she drank it, Kelsey could've had a medical emergency and died, leaving the baby likely to die too..... poisoned or not, I bet that coffee went down the drain. Would you drink something a random stranger delivered to your door?
When PF called her to come clean up the mess, implying it was her fault, she chose to drop everything and come a'running. That would've been a good time for a hard no. And a good time for an easy call to LE. But if not then, how about when she arrived at Kelsey's townhouse and saw the violent bloodshed? And if not then, how about when she was cleaning Kelsey's blood off Kelsey's baby's toys or throwing out a baby bible because it was just too bloody?
I'll tell you why she didn't. IMO. Because again she'd do anything for a friend. PF was her friend. Wink, wink. Friend who gave her the giddy ups. AND because, showing even more awareness of right and wrong, she had to know that, if she called the police on him, he'd rat her out for her failed attempts. What an ugly little jam she'd gotten herself into.
Solution, clean up the mess, cover for PF, bring him some Sonic, watch him burn his beautiful girlfriend, help him destroy evidence, help him to impede LE (Kelsey's cellphone), knowingly leaving a now motherless baby in the hands of a murderer.
She was a nurse. A mother. You don't kill people. You don't cover up murder.
But she knew that.
May she be haunted by what she did. Haunted. Every minute of every day.
JMO