Is it a sin for a woman to cut her hair?

Answer:

"Does not even nature itself teach you that if a man has long hair, it is a dishonor to him? But if a woman has long hair, it is a glory to her; for her hair is given to her for a covering" (I Corinthians 11:14-15).

"Long" is a relative term. God is not dictating a specific length of hair. Instead, he insists that men's prevailing hairstyles are shorter than women's. I don't know of a passage that forbids a woman from cutting her hair.