(((Steph)))
I'm sorry that you had to listen to that from someone you care about. I'm afraid that she was reacting instead of responding to the news. Maybe she will come around after a few days of considering the circumstances. However, she may choose to believe his lies and live in her own denial.
The legal system believes you. We believe you. Your dad believes you.
Be gentle with yourself. You can vent your frustration here and with your Alanon friends. You may want to write a letter to her explaining the circumstances, but not mailing the letter. The writing is a form of therapy for you. Your words won't change her mind, only her understanding will change her thoughts.