Flurry Heart and Ocellus- being Princesses from outside of Canterlot- aren't particularly used to Grand Galloping Galas. Ocellus was always shy- and even if she got better thanks to her friends, still finds it hard to speak up around large groups of people. Flurry Heart may be more social, but she still feels overwhelmed- almost like a sense of imposter syndrome.
So, it was no wonder the two of them found eachother hiding away from the party in one of the many hallways. They managed to find escape from noise and the mixing of commonfolk and high-class citizens, and they felt a sense of peace that, at least they weren't alone in this situation.