Nationality status form (NS form) application

I have a situation which I hope members can clarify for me before I go ahead with submitting a nationality status application form.

The case revloves around my mum's nationality status.

The situation is a follows:

My mum was born in Cyprus in 1951. Cyprus at the time was a British colony. Her dad - also born in Cyprus - was in the employ of the RAF as an auxiliary policeman either just before or just after her birth. He also served in the Cyprus Regiment during the Second World War. Her mum was also Cypriot born. They were both born in 1910.

Long story short, her mum passed on in early 1960 and so her dad left Cyprus with his two kids for the UK in the middle of 1960 before Cyprus's independence in Aug 1960. Entered in his passport was my mum and her brother. The passport was a British passport issued by the local authorities in Cyprus.

They lived in the UK for approximately 2 or so years during which time her dad remarried. His second wife was also Cypriot born but had been living in the UK for around 15 years before she married. She was clearly a full British citizen according to current terminology.

They then left the UK for South Africa but this time the two children (my mum and her brother) were entered on their step mothers passport and not their dad's. The passport was a British passport issued in the UK.

My mum has remained in South Africa ever since and has not travelled abroad. She therefore has no passport of her own and the only documents that attest to her nationality,place and date of birth are the passports that she was entered in namely her father's and her stepmother's. (We have in the meantime obtained a duplicate birth certificate from the current Cypriot authorities.)

Before her dad and stepmum passed on they were issued with British passports for the last time in 1977. Their nationality status in those passports was described as 'British subjects: Citizens of the UK and colonies'. Also indicated in their passports, on page 5 I think, was the term 'holder has right of abode'.

Thats the story then regarding her nationality background.

My questions therefore are:

1) What is her nationality status based on the given information?

2)If she does qualify for British nationality which type of BN would she be most likely to get and on what basis?

Thanks to anyone that may be able to assist