Her changes were advancing rapidly.
Her body lengthened, muscles bulged, hair growing, mane coming in, and all the while, Amy licked your slit hungrily. You wanted to protest, wanted to get to the pen to try and stop this, but as your body came into its own, the pleasure she was providing was interrupting every thought you had.
When you thought you could reach over her, to the desk where the pen was, the counter was pushed back by her growing legs. You reached but could not overcome her new length.
Finally, she pulled away from you but only because her face was pushing out like yours had. Panting, you stumble forward onto the counter. You're out of breath from the change and the joys of Amy's lengthened tongue. Meanwhile, crawling around on the grass behind you, Amy's old body was becoming unrecognizable. Her breasts were absorbed into a chiseled chest, her yoga pants, which had so far stretched admirably, were tugged down by her new tri-hand, to allow her throbbing horse members, which you had hoped to have originally, to breathe, and her hair grew back to allow her mane more space.
Your wits were coming back as Amy, now almost to full stallion, was slowly rising behind you (in more ways that one). You were bent over the counter trying to work the pen between your new fingers. Unknowingly, you had presented your rather perfectly to the reformed Amy. She still was madly attracted to you and, with your rump up, tail flicked to the side and pussy still dripping, you made an appealing sight even if you didn't yet know it.
'Change me and Amy back to how we were when we first met.' You finally managed to write just as Amy finished. You folded it over and went to put it in the slot when a sudden squeezing sensation, of two anthro horse hands, caused you to drop it just short of its goal.
You looked back.
There was Amy, in the body you had hoped to have. White chest with a brown spotted back. Well endowed. While nothing in her old body was there, you could still see Amy in her eyes.
'Please,' you pleaded, 'don't do this.'
Amy lifted her stiffened member. It was aimed right at you.
You may have had the body of a mare but your mind was still the same game you walked into that tent with. The idea of what was about to happen, to be fucked by a stallion as a mare, was really beginning to frighten you.
You try and struggle but Amy is stronger than you.
'Oh no, you aren't going anywhere.' She snorts in a deep baritone.
You try to cry but the first thing that comes out is a whinny.
'Please, Amy, I'm a guy.' You say this even while the entirety of your torso is supported by your melon sized tits. 'You're a girl.' She wasn't hung like one.
She plunged herself, forcibly, into you as far as she could manage. You squint and try to hold it in but another whinny escapes. It feels amazing but a little voice in your head is screaming. Amy continues to trust and pound into you.
Off in the corner of your vision, you see a mirror. In it, you can see yourself, and Amy, and your predicament. You had never thought this could happen but you had screwed things but royally. A single tear went down your fuzzy cheek before you simply gave in to the feeling.
When it's finally over, you had a decision to make.