Possible typo: "I'll send the mirror to the princess. They'll know what do do!" "Princess" is singular, "they" is plural. Did you mean "Princesses", or is Twilight invoking the "royal we"? (those last two words probably will not translate to Russian very well)
Well technically yes, but with how the rest of the sentence is worded it doesn't seem to fit right. Usually if you wanted to use send the passage would go like this "I send Spike out to grab some ink, and then what? He doesn't come back!" I'm not saying you're wrong, just that it could have been handled better. Then again the artist is Russian, so English is probably not his first language.