Biryani turning out slightly bitter after taste.

Both my mother and wife make good biryanis. My mom's biryani comes out orangish color and I love it. While my wife's biryani comes out greener and has that slightly bitter after taste. I asked her to reduce mint leaves, she said she put less. Is it coriander or the star anise+cinnamon+clove that is giving this taste? She grinds the star anise+cinnamon+clove.