Magic:Witch and Unciorn: Can remember the girl's name

I read this book when I was in like 3rd grade. I do remember that the girl's name was Sarah. She has a witch mother and she finds a unicorn. HELP!!!! I LOVED this book so I want to remember it.

Yes, but what year was it read? Was the book new or older at the time? It is difficult to search without a year range! Chapter book or picture book?

Sarah's unicorn
Author: Bruce Coville; Katherine Coville
Publisher: New York : Lippincott, ©1979.
Series: A Lippincot I-like-to-read book
Edition/Format: Book : Fiction : Juvenile audience : EnglishView all editions and formats
Summary:
Although she tries to keep her friendship with Oakhorn a secret, Sarah's wicked-witch aunt finds out and is determined to rob the unicorn of his magic.
Cover.

OMG! Thats the book!!!!!! Thank you soo much!!!!! My sister and I loved that book when we were in elementary school, but we never could remember the name. I recongized the cover though! THANK YOU!!!!!!