How should roommates split groceries when one shops and the other hardly eats at home?

My roommate held up the supermarket receipt and said, "Half is $45. I also did the shopping and cooked twice."

We agreed to split shared groceries equally when we moved in. Lately I've been working evening shifts and taking food from my own meal prep. Last week's $90 shared shop included ingredients for four dinners. I joined one of those dinners and ate some bread and fruit. My roommate ate the other meals at home.

I suggested buying our main meals separately and keeping a small shared pot for milk, bread and similar basics. She said that would leave her doing most of the shopping while I helped myself to convenient bits. That stung because she does know which cupboard needs refilling, and I've mostly left that work to her.

I don't think $45 reflects what I'm using now. I also don't want to reduce her cooking and planning to a dispute about how many slices I ate. What agreement could acknowledge both the changed food use and the work she's been doing?