Cat being extremely picky with food, losing weight because of it.. advice please

I don’t know what her problem is, we’ve tried like 3-4 different foods in the last couple months and she’ll eat it at first then decide she doesn’t like it anymore .. same deal with wet food. I bought her a case hoping it would appease her more but after a couple weeks she decides she doesn’t like it anymore.. I really don’t want to have to transition her food so often but starting to get worried that she’s losing weight. She literally sits there glaring at me by her food bowls once she’s had enough of it, I fill it with fresh food she’ll sniff it and go sit on the corner of her table and glare at me again🙄 like she would rather starve then eat her food. My other cat has no problem with eating it, I keep it in a sealed bag. Fill their bowls with fresh food and water everyday. They each have their own bowl for eating.. so I’m lost.. What do I do???