I had asked Alex if he'd like to help Lia by taking a bath with her and showing her how to do it without crying. (Drawing on his past of various bathtime traumas, I thought he could empathize with her).
At first he said no, but then as soon as Lia was in the tub and voicing her displeasure, he pops into the bathroom, sheds his clothes and hops in the tub.
She wasn't buying it at first but eventually she started to play with him a little and had some fun splashing around. Then I had to rinse her hair and the fun was over.
I don't know if I would go so far as to say she enjoyed her bath, but it was a definite improvement.
And Alex wins the award for big brother of the night.