Oh i didn't know Vivi was THAT dependent on her ex Jesus
normally, I would suggest the tried-and-tested "get what you want to eat/cook", but for someone that has literally never done so before, canned soups and protein shakes are your friend until you learn how to grocery shop + cook proper
after that move up to cuts of meat, vegetables, rice and beans, bread + spread (mayo, ketchup, mustard, relish, etc), fruit, nuts, dairy (milk, yogurt, butter), eggs - but, again, this is just a generic list and will most likely be heavily modified once she finds out what she wants to eat on a regular basis
find a recipe or two to meal prep once a week, so that you have most of your meals all ready to go for the rest of that week, and get the items on the list for the amount of servings you'll make. use an online calculator if you need to, or ask one of the staff at the grocer to assist if you are really bad with numbers
don't just gorge yourself on pizza rolls and tendies in the air fryer, that should be a once-a-week thing at most, or whatever comfort foods you want to eat. you may think you have a magic metabolism, but it'll catch up to you sooner or later