William Green - Parentage of Harriet Green

I can find no evidence to support that Harriet is the daughter of William Green and Sarah Ann Bryan. Can anyone help me here please?

I am reasonably sure that Harriet was born on St Helena, her Information of Death form says so, and the burial information also says so, but her Death Notice says born Cape Province. There is also evidence of her travelling from St Helena to Cape Town in 1882, two years before marrying Ernest Martin in CT.

But I cannot find a birth record for her in St Helena records, nor English ones, which may prove her parentage.

Any help would be appreciated.