Looking around the living room, Ty can see all sorts of various Western decor all over the house. From the wagon wheel coffee table in front of him, the cowhide couch he was sitting on, and not to mention the decorated cattle skull resting over the fireplace. All of those iconic Western paraphernalia and the paintings of the Southwest that graced the walls of the house really tell everyone that Erin is a profound cowgirl. Which is no surprise to everyone mostly because she has moved away from California. Still, the room has given Ty an idea.
Instead of being a simple cowgirl, why not make her a literal Cow-girl!
Ty closed his eyes and began to start thinking of a wish/will for Erin. 'I wish that Erin gained some cow attributes. I also wish that while Erin is aware of her changes, the rest of the world still thinks it is normal and that her home is changed as well according to Erin's needs.' Once Ty was finished with his wanting, he opened his eyes and got ready to see Erin's anthropomorphism into a semi-cow. "So, did you do it? Did you think of something impossible for me?" Erin asked, who saw the little boy just sitting on her couch with his eyes closed for about a minute.
"Yeah, it probably gonna take a while for it to take effect. I'm still trying to work out how this power works." After Ty's comment on his ability to transform everything, Erin started to feel a major headache in her head and an uncomfortable bloating in her gut. 'That's strange,' thought Erin, 'it is nowhere near my time of month.' And yet, those symptoms are there. Including some new sensations that shouldn't be connected to Erin's assumed period. A funny sensation all over her from her toes to her nose, including some minor pain in her tailbone.
Sure enough, Ty began to see some of the changes he willed onto her. From the little horns that are poking their way through Erin's hair to her skin getting hairier with some splotches of white and black patterns. Even Erin's hands which were tightly gripping the pillow in front of her crotch were fusing together and developing a dark finish to them, almost like a cow's cloven hooves. And that is what Ty can see from his point of view.
As for Erin, she can sense some more peculiarness under her clothes that Ty couldn't see. Like how she could no longer feel her toes in her cowboy boots, seeing how they turned into proper cow hooves. The pain that Erin felt in her tailbone that is still hidden within her jeans is in fact her brand new cow tail. A cow tail that comes with her cow fur coating it and her original blonde hair at the end.
Then there are the more adult changes that Erin is aware of and Ty trying to see. Like how Erin's breasts are getting filled up with milk, which in turn makes her breasts bigger. Now, Erin's wasn't flat by any means, she wore a high B, low C-cup bra. But when the milk began to flow into her milkers, Erin would have to buy some bras online to support her now larger-than-life bust. In fact, her minor breast expansion was so fast to Erin, that she didn't get to her shrinking bra in time to save it from her udders.
Speaking of udders, that bloated feeling that Erin felt at the beginning of her transformation in her gut was her proper cow udder. Not wanting to show off her unmentionables to a kid, Erin is still holding on to the pillow in an attempt to be decent. But that attempt at being decent was failing because of how big that pink sack of milk was still growing. While Erin's new boobs were big enough to easily cover her furry torso, Erin's personal udder has grown to a size that would be impossible to hide. The literal gallons of milk were already beading at the ends of Erin's 3-inch nipples and her 5-inch teats, spraying their milky goodness all over herself, her seat, and the area in front of Erin.
Once Erin's metamorphosis into an anthro-cow was finished, there was no doubt to the humanoids in the room that Ty's powers were real.