Login from another device

Yes, you will have to be able to get the verification code on a trusted device.

In case you can't, try this:

...

Get a text or phone call

If you don’t have a trusted device handy, you can have a verification code sent to your trusted phone number as a text message or phone call.

1. Click Didn't get a verification code on the sign in screen.
2. Choose to have the code sent to your trusted phone number.
3. You'll get a text message or phone call from Apple with your verification code.
4. Enter the code on your other device to complete sign in.

...

copied from: Get a verification code and sign in with two-factor authentication - Apple Support

You'll have to use a browser and her credentials to log into iCloud.com with her Apple ID, to do so.