Wait til she connects the fresh City water hose up to the Black tank flush which is right next to the city water connection. And goes inside and says,''Hey...whats that gurgling sound coming from the toilet?"
Just a warning...when that happens...DO NOT go in and press the toilet flusher lever. If you do, all that pressure gets relieved thru the toilet drain really quickly. And she'll get to clean all the black tank gook of the walls, ceiling, floors, doors, mirrors, shower and all the nooks and crannies. It will take her hours. But hey...it's her own fault...right?