Well, we do know that the portal Star Swirl created might have the transformation spell worked into it to help ponies fit into the human world and vice versa.



After all, when Sci Twi created her own protals in Friendship Games, people could cross them and wouldn´t transform.



Also, if pony Pinkie would´ve been around, she and her human counterpart would´ve waved at each other or something. I mean, Sunset only needed to borrow their magic to use it for herself, so I wouldn´t even be surprised if they actually talked with one another...