Whats the deal with Lillian?

Lillian seems to be the wise matriarch of the family -- not meddling unless necessary, keeping confidences, always calm and in control. When Lillian discovers Pearl’s affair, she is very understanding and gives Pearl a chance to stop cheating before she hurts her family. Lillian doesn’t give away Alison's secret of sneaking to Woodstock, allowing Alison to tell her own story.

There are deleted scenes on the web that paint Lillian in a different light. In those scenes Pearl meets Walker several times after her guilty date with Marty. Lillian must be watching Pearl very closely after discovering Pearl cheating, and surely is aware that Pearl is probably humping Walker in the unexplained hours Pearl is missing. Lillian let’s the affair to continue for weeks before finally calling Marty the Saturday morning of the Woodstock concert.

Marty spends 13 hours driving to the bungalow getting there around 9 PM. For some reason Lillian doesn’t divulge Pearl’s affair to Marty the night he arrives, leaving Marty unaware of anything when he confronts Pearl Sunday. Why is Lillian so hands-off while her family is disintegrating?

Danny is stung by wasps, Pearl can’t be found and Marty is called. Pearl and Walker show up to the bungalow a few minutes after Marty is called. It takes Marty about two hours to drive to the bungalow, if it takes a half-an-hour to remove the stingers, then Walker is sitting and chatting with the Kantrowitzs for an hour-and-a-half before Marty arrives. Lillian is very calm and hospitable, offering Walker coffee, and everyone is having a pleasant, get to know you time when Marty shows up. I wonder how Lillian’s conversation with Walker went. “So Mr. home wrecker, what’s your plans after my son divorces your lover? More coffee?”

It's one thing to be in control, but another to be blithely detached from the reality of the situation.