That's some neat idea. I'm not sure what 'Shy's egg is supposed to be though.
Let me clarify. Character making mistakes, and learning from them, is very important. However, when characters commit a flaw that contradicts what has been established about them, it is a problem.
From TT123, we learned that Dash takes note of everything when she flies, and considering her speed, she must be capable of processing information at a very fast rate. This was consistent with Wonderbolt Academy. When her friends fell, she immediately dived straight down to build momentum, knowing there's a tunnel right beneath her, and quickly gathered enough cloud to catch her friends, which again required her to know the quantity and positions of the cloud before choosing that option. Also, she was never one who forget her friends in favor of her interest. Shadowbolts offer, Wonderbolts dream, enough wingpower to beat a record, nothing ever made Dash lose sight of her friends. So how did a book distract her enough to agree to selling away her friend, and took her a minute to process it?
Pinkie may be an airhead, but she is still sensitive about others' mood, shown in Griffon the brush off and especially in Pinkie Pride, even when she focuses on outdoing Cheese. And she should be, if she's really as adept at making people laugh as the show implies. But then we have this scene.
How did she not notice the filly cowering before her? And it's not just this episode, Filli Vanilli as well. In those instances, she was just like one of the FUN! FUN! FUN! clones from the mirror pool.
As for Rarity and AJ, when they insist the other to take all the items to prove "I'm the better friend" comes off as really petty, more so when they try to take for themselves. Or maybe it just rubs me the wrong way. But we just had Simple Ways, where Rarity acted in a very insulting manner to AJ, and yet AJ was still more reasonable than this episode.
And Twilight originally wanted to trade the books away because the library was running out of space, yet she decided to keep them. To me at least, Twilight would be more of the type to give away the books so that others may also learn just as she has, instead of hoarding them out of sentimental values.