What i still can't answer myself is... Did she master her one special talent, magic, with the help of her friends, or did she "master" friendship and to proof this, "created new magic", like Celestia called her actions in MMC in the show?
The second one would be lame. I mean, that would be like her friends are not as good friends as her...am I wrong?
The first just fits. She still doesn't know by herself, how it is to be a ruler. And so, she can still learn things. And I think she can stil learn things about friendship. If she's now something like the "literal-best-friend-ever", what point would there be in letting her stay in Ponyville, than just to wait until she gets her own "Chrystal-Empire" to rule, right?