OP here - thank you for the replies. I did not mean to convey resentment in my question and I blame it on lack of sleep with a new baby, while transitioning back to work

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Thank you for your replies. I agree that this issue is being driven by my MIL which is why I asked for opinions via the site. I've started to stock more of the foods that she seems to like to eat. Also, every day that I've been out I've asked her if she wanted me to pick her up whatever I was eating.
Thank you for all of the great replies!