It's great that you're doing better! I would definitely continue using the cross-ties. We have a couple very girthy horses, and the cross-ties prevent them from nipping you. I second slapping to help stop her behavior; I've never seen a horse react violently to a slap.
If it's any consolation, I walk behind horses much more than is safe, and none of the 90+ horses at my barn have even come close to kicking. As long as you let them know you're there, they should be fine.
As for the washing, I leave them out to dry, them groom them afterward.