The truth

You may not be the element of honesty but you are an honest pony and you decide to tell Twi the truth. "Yep." you put a hoof on Aj, stoping and quieting her angry yell as you gesture Twilight to follow you.

You lead her into your room and take the Smarty Pants doll out of a drawer. Twilight holds out a hoof expectantly but you do not hand the doll over. "You know Twi, I have wanted one of these since I was a colt. I was kind'a dumb and she was so smart, and I thought having such a smart pony as a friend would make me smarter. I saw an opportunity to snag it after your spell ended and all the other ponies in town were leaving and I took it, I'm sorry."

Twilight seems dumbfounded "Mac.. you talked?" You look down ashamed "Yep." Twilight smiles and almost giggles, she kisses you on the cheek as she takes the doll. "You don't need a doll Mac, I am your friend and if you want you can come down to the library after work and I will give you lessons in a few things that I think you will enjoy."

Twilight leaves with you still blushing, and it is only in retrospect that her offer sounded suggestive.