DD went through something like this. After her baptism she developed a fear of the bath. She screamed as loud as she could when I tried to bathe her. I didn't give her a bath the first time but, after that, I was decided it was best to not show her that there was anything wrong with the bath. So I put the baby tub in the regular tub, as usual. Put some toys in the tub but no water. She kept getting up, wanting to get out. But I held her while she was in the tub, telling her "It's okay, honey" and talked to her calmly. She finally sat down and started playing with the toys. I slowly put some water in the tub and bathed her, but didn't wash her hair. Repeated it the next night and, soon, she was crazy about baths again.