Am I the jerk here?

Aunt: I'm going to Walmart, do you need anything?

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.