So Crazy, Its Making ME Crazy

So the last few days have been horrible (what else is new?), and I hate it because its just silly stupid crap but I just can't figure out why she's doing it (she is her: the mother in law). Its stupid stuff like last night, she comes downstairs where I'm working on a project, and says I need to come make my kids something else to eat because they're not going to eat what she's making (okay, side note here; first of all, the whole dinner thing is totally ridiculous because they're old and literally eat at 4:30. FOUR THIRTY. None of us are hungry then, but MIL insists that we all have a sitdown dinner EVERY. SINLGE. NIGHT. But yet, doesn't check with anyone about what they want to eat or anything sort of reasonable. Grrrrrr. Trying to move on.), so since I'm the "wife" (my husband was sitting there doing absolutely nothing) its my role to go make the kids something else to eat. Whatever. I get up there and my father in law is putting chicken nuggets on a pan for the kids, and she literally stops him and says "No, Addison's going to do that!" Like, seriously? What the crap? I don't even know how I'm supposed to take that, what does that even mean? Does she think I'm so lazy that I had better do atleast that? Or WHAT? So then, I'm cleaning up things around the kitchen, clearing the table off, etc. etc. waiting for the oven to heat up so I can put them in, and before its even close to being hot enough, she snatches up the pan and says "I'm just going to put these in here now!" WHAT? Like seriously? Why did she tell me I had to make something and then not let me do it?! What does it mean?! What is wrong with her?! I'm seriously going absolutely insane here. And every freaking word that comes out of her mouth makes me want to scream. I can't even look at her anymore, I hate it. I don't want things to be like this but I honestly don't know how to handle it or what to make of it. Any advice would be much appreciated, especially if you live with a crazy, manipulative, horrible woman.