I think this is the same OP that posted in jobs about how she couldn't make a standing meeting b/c of school drop off and then later revealed she has extreme difficulty accepting help.

Maybe the OP just really doesn't like the friend but doesn't know how to say no and would feel bad doing so because she recognizes it's a nice gesture but really doesn't want to eat the food or spend time with the friend. By not saying thank you she is passive-aggressively trying to end the dilemma.