All of the ‘compact’ dishwashers we can find are 18 inches wide, which is (obviously) a full inch too big. Do you know where (website, store, etc) we can find a compact dishwasher smaller than 18 inches? Places we’ve looked: Ikea, Sears, Home Depot, Lowe’s, Amazon. 10 pts to the best internet sleuth. 
har har, really ‘clever’ answer. She’s only been hand washing dishes for say….40 years. She’s getting older and would like to enter the 21st century…
how about washing dishes in the sink?
Try these links
http://www.epinions.com/reviews/Haier_America_Compact_Dishwasher
http://www.mysimon.com/prices/bosch-srv53c03uc-17-in.-built-in-dishwasher
http://www.mysimon.com/prices/frigidaire-fmb330rgb-17-in.-built-in-dishwasher
Does your friend have enough counter space to use a countertop model? Amazon has quite a few of those listed on their website. You could also try looking at portable models, since they come with casters and you can roll them out of the way when they’re not being used.
Go down to the local home improvement center and tell the illegal laborers on the corner that you need a skinny girl to wash dishes. They will send one of their daughters over to stand there and wash dishes for you.
Be prepared to pay union scale though. The urban myths about illegals working cheap is just that, a myth.
I don’t think she’s going to find one that narrow. Countertop is one choice, portable is another if she has any floor space it could go in. I think even the countertop models are wider than 17″. The portable ones can be wheeled around though I don’t think I’d want to wheel one around a lot. I put mine near the sink and use the top as counter space. It’s a Danby, 17 and 3/4 inches wide.