There's a joke about a lit zippo and a fast getaway in there somewhere. Seriously, air it out as much as you can and put a whole box of laundry dryer sheets under the seats.
Likely going to have to get the hydrocarbons out of the carpet. Once the fuel is dry, a WET shampoo and a WET vaccum. I stress wet here to aviod the zippo and fast getaway approach...then buy her a dozen of those little pine tree air fresheners...Good luck Oxy clean might be worth trying in this...
i am not sure if it will work on gas but the oil company service guys carry a speedy-dry like powder that kills the smell of fuel oil. eventually warm days with the windows open the smell will go away.
coffee grounds (unbrewed) or charcoal briquettes will absorb smell. place either in a bowl in the floor and let it sit for awhile.
Open a Can of Folgers and cut an Apple in half. Let them sit in there overnight and the problem will be solved, side effect it smells pretty damn good in there for a while. Tim
Get some orange base citric acid to cut the petroleum, and leave a nice orange smell, then wash it with soapy water and then with hot clear water. That will really cut the smell and air freshener afterwards should do the rest.
Dont use Simple Green .... the smell of that crap will mix with the gas and you will smell it forever and never want to use simple green again ... for anything , ask me how I know.