Super annoyed

So we live with my fiance's mom. Pay rent, all of that. She's always commenting that we need to get our own food. We got food, and she started saying not to eat the food she buys, and that we should pick better things (we got baking items as well). We weren't really able to get enough stuff for us to be able to be not eat her food, so we got food stamps. We only get $140. She goes and gets her own shopping cart and gets $20 worth of stuff. Since we do eat her food, I'm willing to get some stuff, but I wasn't getting all of it. She gets mad, saying she always gets stuff and that the stuff she got was only a dollar so it wasn't a big deal. I still got a majority of what she wanted, causing us to have less than $100, but she's mad I didn't get everything. Am I wrong?