How do you avoid eating someones food without hurting their feelings?

ok the situation is theres this old lady i help out because when her son moved out she didn't have anybody to help her out with yard work and stuff like that.so ok one day after raking up leaves out of her yard she invited me in for dinner and i was gonna say no but i didn't want to hurt her feelings or anything so i said yes.ok i went inside to wash my hands when i saw her working on the salad or cole slaw or whatever but when i turned around she was mixing the stuff with her bare hands.at that moment i wanted to to run out the door but i said no that would be rude i told myself that i wouldn't eat the salad stuff.so i'm sitting down and her dog comes in and she starts feeding him right at the table and then uses those same hands to serve me up some weird looking meat so after that i had to find some excuse to get out of there. so i mashed the volume button on my phone to make it sound like it was ringing and pretended to have a conversation with someone who needed me to leave luckily she bought it and when i was walking out the door she said"i fix you another dinner next time"i said ok and ran. i want to help the old lady when i can and not be rude to her but how the i keep from having to eat her food?