Liz, I'''m sorry but I don't think baths should make any kid sputter, boy or girl. Maybe you can talk to DH about this?
Deny, perhaps it's GD's clothes and not her body? Anyhow, would her mother/your DD be ok with it if you spritzed GD with some kind of light body spray? You could make it a "beauty" activity that you and she share, as you could put some on, too, so she wouldn't know you think she smells bad.
Or hey, would DD mind if you bathed GD yourself? Have you asked?
Bought the wrong Hot Cross Buns 😩