What is the ruling of Islamic law regarding my marriage to a Baha'i girl who has embraced and committed to Islam, knowing that her family remains Baha'i, and my family rejects this marriage?

If the girl is committed and religious, the son should try to convince his parents. If they are convinced, he may marry her. But if they are not convinced, then obeying them takes precedence, because disobeying them is among the grave sins that lead to perdition. And Allah will compensate him with something better.