help! G.D. frightened of bath

Perhaps she is not keen on running water or water on her face.
Could her DP run a very shallow bath and put in bath toys - or let her throw them in herself, eg ducks and those submarines, frogs etc that can be wound up then go off across the water? She may want to then get in and play with them.
Have they tried bubble bath as well?

If she does decide she wants to get in and play, just let her splash around and don't try to wash her or wash her hair.
She'll be clean enough after a few minutes in the water with some nice gentle organic bubble bath in it.

With the summer and the good weather coming perhaps playing in and out of a garden sprinkler and in a (small) paddling pool will help her overcome her fears.

Our local swimming pool has a row of showers beside the pool, if your local pool has anything like that could she be encouraged under a shower by seeing lots of people,including children, around her doing the same thing?