Be patient, even though you said you're already doing that. Instead of trying to teach her how to put on the gas and let out the clutch simultaneously, have her rev up to like 1500-2000 RPM and keep it steady, then slowly let off the clutch. Not great for the car, but it will allow her to find out where the clutch releases and she starts to move forward. After she does that a few times, try to get her to do it without revving it up first. Tell her it's important not to just drop the clutch all at once, but to be smooth, unless you want your car doing some interesting dance moves.