Hi, my name is ***** ***** welcome to JustAnswer!
If she doesn't remember her username, she at least has to remember the alternate e-mail address or mobile number that she registered with Yahoo when first creating the account. Without that information there would be way to recover the account. If she can remember that info, then you'll want to start here:
This link will take you to the Yahoo Password ***** Page. It's going to ask you some questions and, provided you have the necessary information, it will allow you to recover the Yahoo ID and reset the password.
If you do not have the required information to reset the account, then I'm afraid all you can do is create a new account. To do that, you'll want to go to the following page:
You will then be able to create a new account and set a new password.
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