Uh...both parties willingly entered into a Civil Union and both parties previously came to an agreement regarding custody and visitation.
As adults in America, we must be held responsible for the contracts we sign and claiming to change our sexuality and religion does not void those contracts.
This is not a normal contract case. It would be morally wrong for this mother to allow her daughter to be molested by her former lesbian partner. Would you subject the child to sexual abuse just to punish the biological mother for the bad decisions she made in the past - for which she has since repented?