In Ch. 6, the family of ladies arrives at Barton Cottage. They are cheered up by the servants' happiness at seeing them, but they also each resolved, for the sake of the others, to "appear happy."

So it seems that Marianne is not always obliged by her philosophy or her dramatic emotionalism to ignore the comfort of others and indulge her own excesses. She can, for the sake of her loved ones, exert herself. When she chooses to.