The tiara upon Princess Cadence's head is heavier than it looks. Burdens and expectations rest inside each little gemstone, but she's carried them all her life with ease. Everypony agrees that she is the epitome of goodness: she's always helped those in need and never spoken ill of another pony. She's never even sworn.
So nopony would blame her for being a teensy bit naughty on her bachelorette party.