Speaking on Thursday a coroner in Chelmsford said acute opiate poisoning was the medical cause of death, however, it would probably never be fully understood how Charmain Speirs, who was pregnant at the time, came to her death.
Talking about how the recording of "open conclusion" will impact her daughter's widower, Linda Speirs said: "It is still hanging over him. It's open, so it will hang over him for the rest of his life."
Speaking outside Essex Coroner's Court, Charmain's mother Mrs Speirs said the inquest, which was led by Senior Essex Coroner Caroline Beasley-Murray, was "done well", but "didn't go into great details".
The body of Charmain Speirs, who had travelled to Ghana with her preacher husband Eric Adusah to attend a religious event, was found in the bath of a room at the Mac-Dic Royal Plaza Hotel, Koforidua, in March 2015.
Mr Adusah, who worked with Ms Speirs at the Tottenham branch of Global Light Revival Ministries in London, was charged in Ghana with his wife's murder, however, insufficient evidence led to the case in Ghana being dropped last October.
Ruling out possible conclusions of unlawful killing, suicide and accidental death, Senior Essex Coroner Caroline Beasley-Murray said: "We shall never quite know what happened. There just isn't the evidence."
The inquest at Essex Coroner's Court heard how Charmain's body was discovered two days after Mr Adusah returned to the UK.
Premier has learned HM Senior Coroner has no comment to make in response to the claims by Linda Speirs about her daughters' inquest.
After growing up in Scotland and spending a number of years in Swansea where she worked for the NHS, Ms Speirs lived on Ronald Drive in Rayleigh, Essex.