Win10 App not working after Reinstall

@timperkins Sounds like the newly installed app has found your wife's old 1Password database and so is expecting the old master password. First check that she can login at 1password.com with her new master password and that all her data is there:
https://my.1password.com/signin?a=new
If so, you can safely reset the Windows app:
https://support.1password.com/cs/starting-over/
Open the Windows app and it should ask for her username, secret key and master password.