What's the best dog food for a picky chihuahua?

My chihuahua is extremely picky! She eats cesars dog food but only the chicken she doesn't eat any of the other flavors and I want to get her off that food. She doesn't like anything! She doesn't like treats, hotdogs, or cheese she's weird... If I want to teach her a trick the only thing I can use is chicken... What dog food can I use for her? Hard food? That is very nutritious and number one ingredient is meat? Thanks!