My sister has been vegan for many years and she is also raising her son vegan. He has been vegan since birth. My nephew and son attend the same school so I pick them up from school everyday. My nephew has snacks + dinner at my house every weekday before his mom comes to pick him up. 

I usually make a dish for my family and a separate vegan dish for my nephew. A couple of months ago I left them with their homework and snacks and went to do some chores, came back and found nephew &amp; son sharing chicken nuggets. I provided him with vegan snacks but he still ate the chicken nuggets. I told him those weren't vegan and he told me he that he eats meat in school sometimes. His friends share their meals with him sometimes. I thought about telling my sister but decided not to. 

So basically I continue to give him vegan options but don't say anything if he chooses the non vegan option. Usually he goes for the non vegan one. Maybe because because he never gets to at home. I know my sister would freak out if she knows he's eating meat. She's staunchly vegan and eating animal products goes against her ethical beliefs which I completely understand and respect. My husband thinks IATA for not telling her and being dishonest, but I think nephew is old enough to make his own dietary choices (he's 10 this year). 

So, AITA? Should I tell my sister what's going on?  