US national born to English mother in USA

Hi, this may be a question already asked,but for some reason I cannot find the search function! (rookie error I am sure)
My partner is a US national, born to an British mother in 1972 in the US.
Her mother was born and married in the UK, her grandparents on her mothers side were also British, to a US serviceman, and my partner returned here with her parents at a few months old and lived in the UK for 10 years, before returning to the US.
My question is: Can she apply for a British passport by descent?
She has been in the country for a month, with me, and we would like to get married and live here ( I am a British national)
Thank you in advance for your patience and any help you are able to give.
Regards
Mark

As her father was not British she is not automatically British but it seems she can become a British citizen through naturalisation/registration process assuming her mother was born in the UK and given the information on the GoV.UK website regarding people born before 1st Jan 1983:

If you’re not automatically a citizen
You may be eligible to apply for citizenship if either:

•your parents were not married when you were born
•your mother was British, not your father

Your mother or father must have been a citizen of the United Kingdom and Colonies when you were born. They must also have been one of the following:

•born or adopted in the UK
•given citizenship after applying for it in their own right (not based on having a British parent)
•working as a Crown servant when you were born (for example in the diplomatic service, overseas civil service or armed forces)

Boasleyboy wrote: ↑

Sun Aug 04, 2019 2:31 pm

Her mother was born and married in the UK

Boasleyboy wrote: ↑

Sun Aug 04, 2019 2:31 pm

My partner is a US national, born to an British mother in 1972 in the US.

Your partner would be able to register as a British citizen using Form UKM (Guidance UKM). The fees are £80 (+19.20 for the biometrics) and your partner will need to submit their mother's birth certificate and their own birth certificate as proof.

Note that any children already born to your partner will not acquire British citizenship automatically.

Thanks for the advice!
Really appreciated.
Mark