We flagged down a guy in a big, heavy-duty truck who had a tow strap. He pulled her car up onto the road (i.e. level), where we managed to fill it up to the point that it would start. Her boyfriend arrived at that point, and so I thanked the truck guy, and went back to my own truck. Even if she runs out of gas again from all the gas that we spilled on the slope, she's his problem now.
Lesson of the story #1 - I need to put the tow chain back in the truck.
Lesson of the story #2 - If I ever run out of gas on a slope, tip the tank side up.
Lesson of the story #3 - If I ever see a car out of gas on a slope, look first to see which side the tank is on before going to buy gas. And hey, maybe just buy a funnel when we buy the gas can.
ETA: Yes, the rain had stopped. We were not acting out a country song, at least. Thank the gods for small favors.
*insert your own expletives here, in gerund format