Ariadne didn't think much about the Slytherin girl's mistake. If she were a Gryffindor, it would have affected Ari, but as it was, the girl didn't care much. It was a bad idea to take any animal by surprise, anyways. So she focused on the other question, related to the Sphinx's age.

'It demonstrates once again that time is relative, and that every creature, magical and non-, including humans, have their own lifespan and aging process. For example, a fly lives-what-one day? In which it is born, matures, reproduces and dies...Humans live around 70-80 years, wizards somewhat longer, and each age, from childhood to seniority, takes a relatively large amount of time. For Sphinxes, it's in their nature to live hundreds of years, but they don't have the same aging process as humans. Maybe maturity represents the greatest part of a Sphinx's life, in comparison to the other periods of development.' Hopefully, that made sense.