I guess that's "Taking one for the team"...
Maybe you could send a link related to the feedback process. This should explain to the client how it works without you having to do all the work.
In the big picture though, she needs the feedback rating more than you do. When you have a higher feedback rating, as you already do, the one neutral feedback will not have a significant effect on buyers, they will end up buying from you anyway, if the item is what they want.