As a princess, Cadence is used to the slog that accompanies any fundraiser. It's not fun for anypony, but it is important. When it becomes clear that Twilight doesn't have the same issues, Cadence feels like she can enjoy herself a little.
Although that doesn't mean that she can't help some ponies out in her own little way.
Light. Fluffy. Shippy. And hopefully a little funny as well. Enjoy.