For you anglophones visiting, this is what the image says:
 
“Oh please, Anon. You clearly said that you wanted to swap bodies with Twilight for a while, as your birthday present. You also have said that you wanted to be my student, just like her. I get that. But you weren’t honest with yourself, dear. Tell me, is it just about magic and a good body. . . or perhaps, hidden desires and identity problems? It’s alright. I can see that wearing that dress makes you feel good. Accept and get used to that beautiful, feminine feel because I heard that the spell is difficult to reverse. . . .”
 
And the description:
 
“I only have to say that you’re Twilight Sparkle. You just wanted to have that amazing and pleasant power, and that purple body for some time. For a week or two, who knows. But it turns out that you also had some other desires. Transsexual desires. You also want to see your purple body in the mirror and ire it. It’s perfectly fine. Celestia and the other ponies accepted that desire and Twilight was sure that she’d spend a long time in your body.
 
“And right now, you can’t help but feel that feeling. . . It’s nice, maybe it’s because you’re wearing that beautiful dress, dear?”