Hi KJinLV,
Thanks for posting. We'd like to make sure we're on the same page so we can offer assistance. To clarify, are you saying you're having issues signing in to an Apple ID because the recovery key was lost?
If so, the options would depend on your exact setup and whether she set up any trusted devices, but if she has access to a trusted device, she might be able to use the steps below to generate a new recovery key: How to generate a recovery key - Apple Support
"Generate a recovery key
You can generate a new recovery key from Settings or System Preferences on a trusted device signed in with your Apple ID.
On your iPhone, iPad, or iPod touch
- Go to Settings > [your name] > Password & Security. You might need to enter your Apple ID password.
- Tap Recovery Key.
- Slide to turn on Recovery Key.
- Tap Use Recovery Key and enter your device passcode.
- Write down your recovery key and keep it in a safe place.
- Confirm your recovery key by entering it on the next screen.
On your Mac
- Go to System Preferences > Apple ID > Account Details. You might need to enter your Apple ID password.
- Click Security.
- In the Recovery Key section, click Turn On.
- Click Use Recovery Key.
- Write down your recovery key and keep it in a safe place.
- Click Continue.
- Confirm your recovery key by entering it on the next screen."
If you need further assistance with this Apple ID, we recommend reaching out to us directly with this link: Get Support
Take care.