Possible conclusions of unlawful killing, suicide and accidental death were rejected at an inquest in Essex which failed to establish how Charmain Speirs died.
Senior Essex coroner Caroline Beasley-Murray said: "Because there wasn't sufficient evidence for any of these possible conclusions, I'm going to return an open conclusion.
"We shall never quite know what happened. There just isn't the evidence."
The body of 41-year-old Charmain Speirs was discovered in the bath of a room at the Mac-Dic Royal Plaza Hotel in Koforidua in March 2015.
She had been staying there with her husband, a preacher, Eric Adusah.
The couple, who worked at the Tottenham branch of Global Light Revival Ministries in London, had been in Ghana for a religious event.
Mr Adusah was charged with his wife's murder, however, insufficient evidence led to the case in Ghana being dropped in October 2015.
Offering her sympathies to the friends and family of Ms Speirs, senior Essex coroner Caroline Beasley-Murray added she was a "striking-looking, attractive woman who had a bright future in front of her, and it's very clear that she was much loved".
A post-mortem in Ghana of Charmain Speirs, who was pregnant at the time, concluded she had died from a heroin overdose but the finding was disputed by her family.
A second examination held eight months later in the UK found there was no evidence of assault.
Speaking at the inquest on Thursday about the finding his spouse had heroin in her body, Eric Adusah said: "I never saw her do anything like that."
Ms Speirs, who had lived on Ronald Drive in Rayleigh, had relatives in Scotland and spent a number of years in Swansea where she worked for the NHS.