Can someone help me with this question about food?

Ok so in a nutshell....I love food...and im not overweight and I dont think I eat alot. However...my best freind always has very small portioned food and sometimes only 1 or 2 small meals a day..and she is much taller and larger than me. Whenever I have more food than her or get hungry and crave food she looks at me weired like..u just had something to eat this morning....like 5 hours ago that was small. She also a few times told me not to be greedy and to consider people in Africa and other countries who are starving. She makes me feel guilty. My parents have italian decent so they raised me on large portions of food whilst growing up..and she is australian. What should I say to her or how should I act in front of her when this happens?