_"I’m saying it may have been brought in with the changeling meant to take her place."_
!http://i.imgur.com/KDVDExz.gif!
Chrysalis hasn't been around to see an existing crib. There is no way or reason for her to make a complete duplicate of a crib.
I'm just going to end this unavailing and pointless argument with this:
Having a very subtle changeling with no focus at all in the background is a very common way to give hints to the viewers for those who pay close attention. This here may have been an example of them hinting about the upcoming episode "The Times They are a Changeling". --Actually, this is also confirmed during said episode. When Spike first encounters this changeling, the following conversation comes to play:
*CHANGELING:* "I was part of the attack in Canterlot during the royal wedding, but I had never seen true friendship like that and I couldn't just steal it and feed off of it's love. I wanted to share it."
*CHANGELING:* "After that, I knew I couldn't live with my kind anymore. I set off looking for love to share, but..."
*SPIKE:* "But what?"
*CHANGELING:* "I'M STARVING! And there's so much love in the Crystal Empire right now, it's what drew me here! But it's driving me crazy!"
*SPIKE:* "That would be from the royal Crystaling."
--
I'll leave you to connect the dots from here.