She is right. Food inflation in the US is running at an 8%+ rate based on the latest stats.
Nearly everything you buy at a retail store is shipped in by truck. The store is probably operating at about 6% margin and can't afford to absorb the additional fuel costs and nether can the trucking company. So the rising cost of fuel is ultimately paid by the customer. That applies to everything and not just food.
Regards,
GtG