A Ring, a Bracelet, and Venus — Shirley Larson

Deborah feels the universe is against her. She wears a back brace and is mocked by her college classmates. Studying is her only escape. Professor Rogen Maris takes an interest in her and she promptly falls in love with him. But he is out of her reach. She asks Venus to take her back to the Middle Ages. Her wish is granted, but not quite the way in which she envisioned.