Hey yaylaliza,
From what you describe, you're seeing the Activation Lock Screen. This is a security feature to prevent anyone from accessing the device in the event that it is lost or stolen. Resetting it to factory settings will not remove Activation Lock. In order to do so, she will need to remove it from her account. This article provides the steps: How to remove Activation Lock.
Once she has removed the Apple Watch from her account, power it off and then power it back on to see if you get a different screen. Afterwards, attempt to reset to remove her information from it by following the steps here: Unpair and erase your Apple Watch. Scroll to the section labeled "How to erase your Apple Watch if you don't have your iPhone".
If you're still do not have access to Settings, try the steps here: If you forgot your Apple Watch passcode.
1. Put your watch on its charger and keep it there until you complete these steps.
2. Press and hold the side button until you see the power button in the upper-right corner of the display.
3. Press and hold the Digital Crown until you see Erase all content and settings.
4. Tap Reset, then tap Reset again to confirm.
5. Wait for the process to finish, then set up your Apple Watch again. When asked, restore from a backup.
Take care.