Diana dated Hasnat from 1995-1997, before her much publicised romance with Dodi Fayed.
Jemima tells how the Princess Diana sought her advice during fundraising visits to Lahore, Pakistan.
'She wanted to know how hard it had been for me to adapt to life in Pakistan', she revealed.
The Princess was reportedly so besotted with the surgeon,that she was keen to marry him and move to Pakistan.
Speaking of the fundraising visits, Jemima added:
'Both times she also went to meet [Hasnat's] family secretly to discuss the possibility of marriage.'
But despite Diana's royal status it seems Hasnat's influential family was another one she found it hard to fall in favour of.
'[For a] son to marry an English girl is every conservative Pashtun mother’s worst nightmare,' Jemima explained.
'You send your son to be educated in England and he comes back with an English bride. It’s something they dread.'
And disagreements over marriage proved to be the sticking point in their relationship, with it ending around the time Diana started seeing Dodi.
Naomi Watts will star in the upcoming film Diana, which tells the story of the Princess' relationship with the heart surgeon.