British nationality law can be maddeningly confusing. The notes on the Home Office IND web site are not as clear as they could be, I fear.
However, from what I understand, British nationality law underwent a big reform in 1982, which came into effect on 1 January 1983.
Prior to the reform, most everyone who was born in the United Kingdom (England, Scotland, Northern Ireland, Wales) was a British citizen, unless the parents were in the UK with diplomatic or consular status. The citizenship status of people who were born here (and whose parents were not Dip or Con status) was "CUKC" or citizen of the United Kingdom and Colonies.
After 1 January 1983, in order to gain British nationality by birth in the UK, your parents had to have "settled status". That means they had to be either British citizens, have Right of Abode, or have Indefinite Leave to Remain. So you would not be British if you were born in the UK after 1983, but your parents were in the UK only on a work permit.
The reason for this change is that in the 60s and 70s, there were so many people in the UK for various reasons, and they were having children here, and those children would then, as British citizens, be entitled to sponsor others for immigration to the UK. It was at a time when immigration had been running at high levels and the government wanted to restrict citizenship for that reason. The requirement that the child's parents have settled status significantly cut down on the number of people who acquired nationality at birth.
However, as I understand it, the 1983 changes were not retroactive. So the further requirements and options regarding registration to which you refer are not really relevant to pre-1983 cases, so far as I know. But this should be checked with a solicitor!
That is how I have understood the distinction of pre-1983 and post-1983 law, but she should check with an immigration solicitor or advisor here before doing anything.
