Iphone needs password after factory reset but no passwords work

in than case all I can suggest is read https://support.apple.com/en-gb/105132

Your sister did not properly prepare it for someone else to use.

Give it back to her. It's useless to you or anyone else until she removes the activation lock.

After a factory reset there is no Lock Screen. There should be a multi language Hello screen - is that what you see?

If not then it has not been reset to factory.

The only passwords needed are Passcode, Screen Time Passcode if set, or Apple Account password.

If your sister has s new iphone ask her to go to iPhone, Settings, [tap her name], and check that her old phone is not on her list of devices.

KiltedTim wrote:

Your sister did not properly prepare it for someone else to use.

Give it back to her. It's useless to you or anyone else until she removes the activation lock.

That was my original thought, but they say it is not in her list of devices and it starts with the Hello screen. Scratching my head to see how it can still be locked unless this is a big fairy tale to unlock a stolen phone.

Then I would guess she was using a different Apple account on it.