Halfway between dog and human, specifically a golden retriever breed.

Sure enough, that next morning, Tom woke up to find his wish had gone exactly as intended. Sarah was still asleep, and he looked at her new form as something of rapturous beauty. Her entire body was covered in thick, blonde fur, and her face looked almost exactly like that of a golden retriever, only with her normal hair coming out of the top of her head, and enough human features to her face to make it capable of making more human expressions.

Tom just laid there, watching her sleep, until Sarah finally blinked her eyes open. She rose from the bed with a stretch, then looked at Tom with a big doggy grin. “Morning!” she said, chipperly. Quickly she got out of bed, and started doing some more stretches. “I don’t know why, but I’ve got a lot of energy this morning.” With her up and about, Tom could see her furry tail, about a foot and a half long, sticking out of the back of her pajama bottoms, and it was starting to wag. “What are you looking at?” she asked, breaking Tom out of his revery, and she looked down and noticed for the first time how she’d been changed. “Whoa, this is weird,” she said, not quickly turning her body around so she could get a good look at all her changes, reaching up with her hands to touch her new muzzle. “I’m like a dog girl!” Then, looking back at Tom, she almost glowed with happiness. “This feels amazing! What do you want to do?”