Pairing Apple Watch with new phone .. can't remember *old* iCloud password.

My wife has an Apple Watch that's connected to her old phone (now dead). She got a new iPhone, erased and reset the Apple Watch.

We're attempting to pair the watch to the new phone with the same iCloud account, but get stuck on the step where it asks us for the username and password for the *old* iCloud password (4-5 years ago, at this point). She doesn't remember that password. She knows the current password to that iCloud account.

Is there a way to pair / unlock Find My, or are we bricked because she won't be able to recall that original password?