Just got back from a second viewing and one thing I'll say about Marta...she obstructs justice multiple times (deleting the security tape, ruining the footprints, trying to get rid of the lattice piece) and leads a car chase from the police. I suppose this all can fit in a certain logic of being too much a heart of gold type, but I'd say it shows a capacity for deceit/selfishness. It is a bit of complication to her character, she just stays ultimately way nobler than the family. And as bad as the family is, I am not sure Harlan's cutting them out completely and giving it to Marta is far to either the family or Marta. We see how the attention of the will creates problems for Marta. His desire to make a game and a lesson of everything is actually a bit of a flaw. And one interesting thing with regards to the grandchildren is you do get a kind of balance of the alt-right troll and the SJW...though notably she is a hollow SJW who cannot see past her own privilege even as she professes the correct views. It is in fair respect a broadside against Trumpism, but it has that bit of nuance that it doesn't actually let people off easily.
On the broader level, it was definitely a less compelling viewing. I don't know that I gained a lot in the second watch and the atmosphere wasn't quite as electric as an opening night film festival gala with director present. Not the most fair comparison. My friend enjoyed it. Still, the other movie I watched twice this year is Midsommar...that did have the advantage of being a directors cut the second time, but I'd say that second viewing was more involving than Knives Out, so it might get the edge.