Thanks everyone.  She drove across the border into Illinois and found a station there that had a small nozzle.  She said it must be the only station with a small nozzle as there were two other people with TDIs waiting for diesel from the one pump.  

We live in the Madison, WI area and virtually every station sells diesel.  Almost every Kwik Trip has at least one pump with a small nozzle.  I suggested to her in the future to buy a 5 gallon can if she needs to and fill that first then into the car. I don't trust a funnel.  The big nozzle pumps can really flow the fuel if your not really careful.