stupid arguments have simple solutions

It's normal to have arguments in relationships. No two people can possibly agree on absolutely everything. How you deal with those arguments determines whether or not the relationship is healthy. I learned all that in Human Relations. So is my relationship healthy? I'm not sure. We tend to argue frequently...mostly over stupid things. I thought maybe I could find a way to prevent those stupid little arguments. I thought if I was more specific when I told her something and if I asked for clarification when I didn't understand what she was saying, it would prevent misunderstandings. Seems simple doesn't it? Did it work? Not really. Take today for example, neither of us felt like making lunch so we decided we should go get something. Being low on money, tacos seemed like a good idea. You can get 10 tacos for $10 at Taco Bell. She said she would go pick them up. She asked me before she left if there was anything else I wanted. I said, "No, just the 10 tacos." She came back with 5 tacos and 5 bean burritos. I was frustrated. I was clear about what I wanted her to get. I said it twice! And still she somehow misunderstood. She said she thought I was talking about meal #10 and forgot that I didn't like bean burritos. I don't get her thinking. All this time I've been assuming that our misunderstandings were because I wasn't being specific enough, but I think this proves that she just doesn't listen to me. So why do I waste my breath? I could just do everything myself from now on. I mean, I can't force her to listen to me or understand me. So why bother? It's just freaking frustrating. She can remember some stupid little thing I said one time 3 years ago and she certainly remembers every single time I said she didn't do something right, but she can't remember what I asked her to get for the 10 minutes it takes to get to Taco Bell? Sometimes I think she does hear me and knows perfectly well what I'm saying, but she just doesn't care because she thinks she knows me better than I know myself. It would not surprise me one bit if she got half burritos on purpose thinking it would be a great surprise that I would love and thank her for anticipating my needs. She gets off on that kind of bent sometimes. She ignores what I say I want and proceeds to give me what she thinks I really want. I'm not that complicated. If I want something I ask for it. She doesn't need to guess. Maybe she just thinks that's how relationships work. She does seem to get frustrated with me if I ask her to be specific about what she wants. It's like she expects me to just know and surprise her. I have no idea how to do that. I don't even know if it's possible. And I'm talking about every aspect of the relationship, not just about buying things for each other. Like I'm supposed to know when she wants a hug. How do I guess that? If she was walking up to me holding her arms out, I could guess. But how to you guess someone is wanting a hug when they're sitting at a computer or watching tv? I'm not nuts to think that's a crazy thing to expect am I?