My aunt is obsessed with food-guilt?

Tell her that you are please to announce that you have no food issues at this time. You do not eat because you are depressed, lonely, sad, mad, feel inadequate or just generally miserable. If you get to that point then you would love to talk to her about it but until that time you would appreciate it if she would just concern herself with her own weight and stop making others feel uncomfortable. Say "Thank you", then say you need to leave because it is now time for you to throw up! Wouldn't want to put those pounds on!