Earlier in the film, Marta told Blanc that she'd originally been hired to be Harlan's part time nurse, because of the medication he was on and that he needed help administering it. The her role was expanded, giving her more time with him, and Blanc asks if it was because of her nursing capabilities. She pauses for a few seconds, and then just says, "He needed a friend." Paints a clear picture of the oldest members of the family being quietly disrespected and not really liked, even if Harlan was sort of a bastard.
What strikes me is the similarities between this and last year's Ready Or Not, minus the human sacrifices. The sniping, backbiting family who present a united front with strangers, but in actuality can't stand each other most of the time. Linda accuses Blanc of baiting her, trying to get her to talk shit about Walt, and of course she theatrically refuses, and then one scene later Richard's saying that Walt didn't really run anything, he was just his dad's errand boy. We never find out what Joni was doing with all that money she was embezzling, I don't think, but Harlan discovering the stealing was just part of him deciding to cut all of his kids off.
I have to give major points to Chris Evans. Ransom's ability to fake being sincere held out longer than Meg's did, since Marta seemed to like Meg up until finding out she's the one who ratted her mom out about being in the country illegally. And I enjoyed the bit about the clock coming into play again - "Who opens a clock?" - about the toxicology report. I think Harlan decided to just end it, though, since Marta did give him the correct dosages by accident. He knew his money and the legacy his books had created would be in good hands with her, and it was a final way to give his mooching kids the finger. Well played, sir.