When screen time battles start over educational apps only

Lately, my 6-year-old has become obsessed with a particular educational app that promises to help with reading skills. The problem is, she insists on playing it nonstop during the hour of screen time we allow, which means she refuses to try any other activities or even other apps I think might be more balanced. I've tried setting timers and explaining that different activities help different skills, but she just argues back and ends up upset when I switch off the app. I want her to enjoy learning but also develop a variety of interests without feeling controlled. We've also tried introducing similar apps together so she feels involved in choosing, but that hasn't stopped the fixation on this one. I'm worried about the frustration building up and the power struggle it’s creating around something that’s supposed to be fun and educational. Has anyone dealt with a similar fixation on a single app or game? How did you help your child open up to other ways of learning without turning it into a battle? Also, how do you balance encouraging educational screen time while keeping it enjoyable and not a source of stress?