My mom says I'm "rude" for doing this...I don't see it as rude?

Perhaps you should offer to make a meal or two a week. On those nights you could be ured that there will be plenty, and that it will be something you like. I think you should ask your mother's boyfriend if he knows any easy recipes from his country. There are many delicious Mexican foods that aren't often served in the U.S. that you may find you like if you try.