I have to admit I got quite a chuckle out of her thinking the potties just emptied out on the road!
I have a friend whose Aunt got the same bee in her bonnet. She spent 60K on a large Class A motorhome that she intended to drive from Indiana to Texas for the winter. Never test drove one- just bought it.
On the way to Texas she swerved into the other lane, and a semi took off her side mirror. It scared her so much that she pulled off the road and refused to go any further.
Needless to say, she lost quite a bit of money on that little excursion.
Best of wishes to you and your wife in your efforts to help! Let us know how it goes.