The partial skeleton of the woman, who was aged around 25 when she died, was discovered last year as the search got underway for the body of Simon Fraser, 11th Lord Lovat, who was executed in London in 1747 following the Battle of Culloden.
There is a long-held tradition that the clan chief - also known as the Old Fox given his double dealings between Jacobites and the State - was secretly moved back to the Highlands by his supporters after his death.
But an exhumation of a lead coffin at the family crypt at Wardlaw Mausoleum by forensic anthropologist Professor Dame Sue Black, formerly of Dundee University, led to the discovery of the woman instead.
Mystery surrounds the identity of the woman and why she ended up in the coffin believed to have been built in London for Lord Lovat, chief of Frasers of Lovat, ahead of his execution.
Now, new details of her life have emerged following chemical analysis by Dr Peter Ditchfield, manager of the Stable Isotope Laboratory at Oxford University.
Using a fragment of the woman’s breast bone, he has been able to determine the young woman’s diet and possible social position.
He found that the woman enjoyed a diet of meat and some fish and shellfish, which suggests that she was from a relatively wealthy background.
Tests have indicated she had a diet similar to someone living in the relatively affluent area of Spitalfields in London at the time, although it has not been possible to confirm whether she did indeed live in this neighbourhood given the state of her remains.
Erik Lundberg, custodian of Wardlaw Mausoleum at Kirkhill, where generations of the Frasers of Lovat are buried, said: “It is fascinating to get a glimpse of the life led by this young lady, and a testament to the skill of Dr Ditchfield in recovering this information.
“Unfortunately, the isotope analysis undertaken by Peter is not able to say that she definitely came from an affluent area of London, like Spitalfields, just that she had a diet like someone from there.
“A person from a wealthy local family around Kirkhill – like the Frasers – may have had a similar diet, or perhaps she is someone that had spent a significant amount of time in London.”
The London connection has also raised fresh questions over why the woman’s body was found in the Highlands. Mr Lundberg said a “puzzle” remained over whether the woman was put in the coffin in London and moved north.
Mr Lundberg added: “The clan story is that, after the execution, the body in the official coffin was swapped and the coffin was brought home, as Simon had wanted.
“We now know that Simon was not in the coffin in our crypt. It is just possible that he came to Wardlaw and was then moved to an unmarked grave elsewhere in the graveyard once word got out that he was here when he shouldn’t be. This would leave a convenient empty coffin for the young lady to occupy.”
Mr Lundberg said he believed it was the case that Lord Lovat was buried in the chapel at the Tower of London and his double-lead coffin brought home and placed in the crypt.
The custodian added: “Could the young lady have been in the coffin from London and, if so, why? Her body would not have made a significant difference to the weight of the coffin to give it credibility as containing Simon, so could it have been a convenient way to dispose of a body many miles from the scene of a crime? If she was indeed a local person, especially a Fraser, why was she placed inside Simon’s coffin and not given one of her own?”
So far, it has not been possible to retrieve a DNA sample from the bones given their poor condition. The woman was reinterred during a special service last summer.