Wow, didn't think this was an issue with women, anyway, I think the problem stems from them not being able to visualize how the water will be spraying from the blades or arms inside the dishwasher. You may have to explain to them that a dishwasher is not like a clothes washing machine where the items to be washed are moving around to get clean. Tell them that it's the exact opposite with a dishwasher. Items stay put so you have to place the surface you want to come clean in the direction that the water spray with detergent will be coming.
After you tell her all that and she tells you to "F..k off Mr. Know it All, you think you are so smart and perfect!", just take her out to eat and hope that she forgets about the incident.