it means that her parents were not marrird and the father did not, would not, or could not attend the registration as only a married woman can add a father's name to a registration of birth in his absence.
It does not mean her mother was a widow, as her mother's name should just be the mother's maiden name. I assume the informant is also the mother? If her mother was or had been married the married name would be there too nee whatever her maiden name was, but that sounds unlikely. The fathers name would have been added with the word deceased in brackets if the father had died before the regsitration.