Me: no thanks, I'm going there later to do some shopping myself
Aunt: But we could combine trips! It's wasteful to both drive there on the same day! The responsible thing to do---
Me: ok, I give up. Please get me cat litter and cat snacks.
Aunt: Ok!!!! :)) Which ones? And what isle? What color is the package---
Me: exasperated Are you serious? I caved and gave you what you wanted. Now you're asking for more information? I told you I wanted to do my own shopping, and you fought me on it. I'm making a peace offering by giving you two items to buy for me, and you're saying I need to go find the names and package colors and isle numbers? Please just be satisfied with what I gave you.
The thing that she wants is to feel good about buying me something. But I don't want that. That's the disagreement.
I imagine most people would see me as the asshole here: she can't buy the right item if I don't tell her what it is. But I clearly don't care about those details; if I wanted something specific I would have told her that. The only reason I mentioned them was to appease her. I'm giving her something she wanted, something I wanted for myself, and she's demanding more.
I understand why you are upset, however, you should have just said
"Because I prefer to shop alone, I don't need anything, thank you"
What people don't get from the prompt is that your aunt is overbearing and constantly finds a way to "help" you but it's really just a way for the person to insert themselves into your life to feel more important/relevant because they can't get in another way or they can't relate to you or there is some past friction. They are the type of people that ask if you are hungry and won't accept 'no' until you give them the answer they want or until you blow up on them, and you're the asshole somehow.
Thank you so much. People are so hurtful here. I appreciate the response, and I agree with you: "I'm helping" is an excuse that can be used to justify bad behavior, such as privacy violations (figuring out what someone else needs), forced compliance (give me something to make me happy or I'll argue at you) or short-term validation. It's a convenient flag to throw when someone gets hurt and you don't want to feel bad about it. I'm so tired.