As soon as I started potty training my two children (daughter is 4 & son is 27 months)I would take their clothes & diaper off & put them on the potty while the water was running. Usually the sound of the water made them go, so it was never an issue once in the tub. She may be just seeing if she can get her way which as you know kids do once they can. I would follow the same routine every single time: take off clothes & diaper, start running water, put her on potty & say Yea! if she goes, then bath. She may protest, but if you are consistent, eventually she will learn the routine. I've also had to make going to the potty before bedtime a regular thing for my 4 year old since the few times she said she doesn't have to go she has wet her bed.
PS. I had to throw away all our bath crayons, cute fun soaps & bubbles b/c it seemed like they were always irritating my daughter, not to the point of a UTI though. So I would recommend going back to a baby wash since they are more gentle than those fun kids soaps, etc.
Hope this helps a little.