Grandmother had UK passport, but was not born in the UK

I'm just starting to research the various visas that I could apply for and I discovered that I have a rather unique situation that I don't think will work for the ancestry visa.

My father's mother was born in Cuba to British parents. She received her UK passport and used it for about 20 years until she was given a Canadian passport, which she then used. letting the UK one fall by the wayside.

She wasn't born in the UK, but would anyone know if she would still be considered a UK citizen? I imagine I'm not applicable for an Ancestry visa, but I thought I would post this to see if anyone had any information or thoughts on this odd situation!

Thanks!

---I think I will be applying for a Working HOliday Visa instead.

your grandparent needs to be born in the UK - she probably is a UK citizen but in order to get an Ancestry visa you need to show proof she was born in the UK - which she wasn't