Newland is crumbling, and so is his illusion of May.
In a tizzy of denial, Newland has fled to Florida in a mad attempt to convince May to bump up the wedding. She is curious as to why and wonders about Newland's loyalty. Her line of questioning is misdirected in its detail, but she is astute in observing that Newland's heart is wandering away.
But, those rare moments where May seems to see through the fog for just a moment are brief and Newland realizes how closed she truly is.
Who should we pity more, May or Welland?
May sees the world as she wants to, as she's been told to see it. That is a pitiable state, albeit it blissfully ignorant. Newland's eyes have been opened and will most likely stay that way for the duration. This is painful, but at least it is real.
Which is worse?
Since this question has been in play since Adam and Eve, I don't expect an easy answer. . . and I doubt Ms. Wharton does either.