Your girlfriend was having a hard time sleeping as you were still asleep, while she woke up to notice why you were moaning so much, as she discovered the size of your fully changed penis while you were asleep, and becoming as equine as possible. While you were asleep, you felt your penis get touched by your girlfriend.
Precum squirted all over the place, including on your girlfriend, but after she tasted it, she ended up in a trance after the cum you had in your new overgrown penis hit her tongue, so she decided to suck on more of it, while also experiencing some changes. First, your girlfriend felt two small teats begin to sprout from where her pussy was, and then felt her pair of breasts grow as well. As the two sets of lumps grow, white fur sprouts around her waist, while a tail with blonde hairlines start to form.