I'd tell her to housetrain the dog, unless there's a reason he can't hold it until he goes outside. A crate would help too. Neosporin isn't a good treatment for diaper rash, she could use some diaper rash ointment if its bothering him, and if he won't lick it off. A band-aid is going to hurt that poor dog like hell when she rips it off. The best cure is fresh air without a wet, textured diaper rubbing on it. A band aid will only keep the moisture in so the rash doesn't heal as well.