do you and this neighbor get along? first I would negociate with him/her to make adjustments so that my house would not get soaked.
If no luck, I would take pictures and document this and consider legal actions.
But in direct answer, I do not know any way to remove cresote from a paint job and still maintain the integrity of the paint. Rubbing with mineral spirits would remove the cre, but would damage the paint.
cAn you build a protective splash gaurd of some sort to prevent this?