Yes, there is a tendency to be amused because Mairanne is overly dramatic but to her, this is the appropriate response to her very real feelings. In JANE AUTEN'S WORLD under the section "The cult of sensibility: is this paragraph:

The earliest of her novels, SENSE AND SENSIBILITY, is a reaction to Jane Austen's youthful reading. The cult of sensibility, which was prevalent in the literature of that time, argued that to have overpowering feeling was a sign of superior character. It followed that is was as wrong as it was hopeless to try to control or hide such feelings, whatever inconvenience or suffering they may cause their owner or anybody else. Jane Austen had two quarrels with the cult of sensibility. The first was that people might exaggerate and falsify their feelings in order to be thought superior. The other was that even when feelings were deeply held and true, they did not excuse their owner from observing the common decensies of social behavior.