There is a good reason Rarity - well, Cherry Spices - never lets anypony in her room until she is awake. It wouldn't do for somepony to stumble upon her if she's... not 'herself' as one might say. Before the last pieces of the costume are in place and proper enchantments in place. Before she is mentally ready to be Rarity again. Although that last part has gotten way easier over the years.
She even sleeps more and more in her costume, finding it confortable enough after years in it. Regardless, just to be safe... no pony enters in the morning and Carousel Boutique only opens its' doors way later in the day.
So yeah, couldn't leave this idea alone just yet.
Some people I am too nice to mention here even have prodded me towards starting a tumblr, maybe based on this idea.
We'll see if anything happens. (Don't hold your breath though.)
Rarity, Those Confounded Ponies (c) Hasbro.