apple refusing to fix phone because find my phone can not be disabled

Apple requires that Find My be disabled for all service repairs. She can try to reset her Apple Account password on the web when you don't have another trusted device to do so, which is at iforgot.apple.com. If she still cannot she will have to enroll in Account Recovery which is a process when the password cannot be reset.

You could refund your AppleCare+, but it still wouldn't mean you can receive service on the iPhone without removing it from Find My. And if you do end up removing it from Find My with no AppleCare+, you will have to pay exponentially more for repair, I'm talking a few hundred bucks for a screen repair compared to $29. And neither should you have the screen repaired by someone else as they do not have genuine parts and will void any warranty which you currently have.

If you forgot your Apple Account password - Apple Support

How to use account recovery when you can’t reset your Apple Account password - Apple Support

FindMy needs to be removed. She may be able to reset her password at iforgot.apple.com. Hopefully she has a different trusted device or trusted number on her account.

For instructions on how to get your iPhone, iPad, or iPod touch ready for service click here --> Prepare your iPhone or iPad for service - Apple Support

Read #4 under: Prepare your device for service. You can disable the feature remotely using a different device or computer.