AITA for asking my coworker to stop bringing me homemade lunches?

I put the lunch container back on my coworker Marta's desk and said, "Please don't bring me another one."

For three weeks she'd brought extra portions of whatever she cooked. The first time I thanked her and ate it because my own lunch was still at home. After that she started leaving a container for me several mornings a week.

I did thank her each time, but I didn't always eat the food. I had packed lunches I wanted, and sometimes the container stayed untouched until I could take it home. I never told her that.

On Tuesday Marta said she was thinking of making my favorite dish and asked what it was. I said she didn't need to cook for me. She laughed and said it was no trouble. When another container appeared Wednesday, I returned it while two colleagues were beside her desk.

Marta said she'd only been trying to include me because I was new. One colleague said I'd made a kind gesture sound like a nuisance. I offered to wash the containers I still had and apologized for putting this one down abruptly.

I don't want meals to become an obligation I have to accept, but my weeks of cheerful thanks helped make it seem welcome. Would a private refusal have been enough, and was I the asshole for waiting until I was irritated?