I would disagree that the caller needs a new compressor or has a leak. I would venture to say that the problem is very likely that when she had her AC charged, that the technician overfilled it based on the ambient temperature. It is probably right at the top of the range. When idling the pressure is too high and the compressor cannot push the freon through the system. I would also bet that it only happens when the outdoor temps are in the upper 90s. At idle the engine compartment gets much hotter and the higher temps puts the high pressure side of the AC into an over-pressure situation. Putting the car in neutral and pushing up the RPMs will not help. It will not fix itself until the car is moving and the engine compartment cools down a little. The solution: get a mechanic to remove some of the freon and verify both the low and high pressure measurements for the ambient temperature.