Ever since she ascended, Twilight has been granted access to spells and magic she never thought she would get to know, or even hear about. However, even to one as gifted in magic as Twilight, there are spells that can still surprise her. Creating a stallion out of thin air for the purposes of being the perfect coltfriend? That is most definitely a new one.
But Twilight, being Twilight, is certain that such a spell is ridiculous. A mere flight of fancy. After all, even if she were to, say, actually attempt to cast it, it's not as if it would actually work...right?