what in the grant of the easement is there concerning the use and maintianance of the easmemnt.

Typically the users of an easement are liable for the costs to maintain it. If it is a jointly used easement, the costs are shared between the users.

Can you simply fill in the drain? If she requires some sort of drainage for her property, unless the original property owner caused the drain to be needed by building the easement, the neighbor may be able to be required to maintian the drain since you have no benefit of it.