Further, she has to remove the defamatory passages and give it in writing the that the allegations in the manuscript are false and will not be there in the book.
Reham also touched on what she called Imran's shifting loyalties which she said was a disturbing trend that voters in the upcoming election needed to be aware of.
Even though the book has not been released - nor scheduled for one - leaked manuscripts seem to have found their way to PTI supporters, who verify extremely damaging content regarding the filers.
She told India's CNN18 television network the book focused on "sexual coercion and how it is used, how sexual favours are used for political positions, for media positions, and some of them are directly related to PTI".
Aside from Jemima Goldsmith's warning, Reham has been served a legal "pre-action defamation" letter by a west London law firm, on behalf of a handful of people including her first husband, Dr Ijaz Rehman, along with a PTI official, a British businessman and cricket legend Wasim Akram. She has said the book will reveal details about their marriage and the inner workings of Pakistani politics.
She did not say that Imran had engaged in sexual harassment but claimed he had direct involvement in "nepotism or favours which have nothing to do with merit".
"We have received no notice to date", said Yasir Hameed Hamdani, Reham's lawyer in Pakistan. According to reports, Jemima on said that though she had been "assured" that Reham's book was too "libellous" to be published in the United Kingdom, she would sue on behalf of her son for defamation and breach of privacy if it did see the light of day. That's the period she has described in her book.
She spoke about the gender divide in Pakistan, saying that being a wife can leave one's "love and devotion worthless" if a man chooses to end the relationship.
Nawaz Sharif was disqualified as prime minister in the Panama Papers case by the Supreme Court under the same provision.
"When I voted in 2013 for Imran Khan, I didn't know what I was voting for", she says, adding that she won't be voting for PTI again.
Reham has also accused Anila Khawaja, media coordinator of Khan's PTI party, of having an illicit affair with him and exercising enormous control over him.
65-year-old Khan's previous two marriages ended in divorce.
Rumours about Khan's third marriage started circulating in January.