Bobbi Kristina, the daughter of late superstar Whitney Houston, died on Sunday after spending six months in a coma - and her death is being treated as a homicide investigation

Bobbi Kristina Brown may be ‘finally at peace’, as her family said in a statement following her death at the weekend – but the conspiracies surrounding the circumstances of her death aren’t showing any signs of settling down.

The 22-year-old daughter of late super singer Whitney Houston eventually died on Sunday after spending the last six months in a medically-induced coma after she was found unresponsive in a bathtub in January.

In a statement, her family said: ‘Bobbi Kristina Brown passed away July 26 2015, surrounded by her family. She is finally at peace in the arms of God.

‘We want to again thank everyone for their tremendous amount of love and support during these last few months.’

However, the story continues as yesterday local authorities informed US gossip site TMZ that they had ‘amped up’ their investigation into Bobbi Kristina’s death, which they are treating as a homicide investigation – with the aspiring singer’s boyfriend, Nick Gordon, remaining a ‘person of interest’.

Controversy has always surrounded Bobbi and Nick’s relationship. The 25-year-old was taken in and raised by Whitney at the age of 12, although she never officially adopted him – and even predicted that he would get together with her only daughter.

The pair eventually went public with their relationship in 2012 shortly after Whitney’s death, and announced their engagement months later.

It was Nick, along with a friend, who found Bobbi Kristina unresponsive in the bathtub in January.

At the time, TMZ reported that bruising found on Bobbi’s body had lead the police to suspect foul play, prompting them to investigate her boyfriend.

Nick was later recorded insisting that it was drugs that had been Bobbi’s downfall, telling a member of her family: ‘I’ll tell you the honest truth, Krissy, she was under a lot of stress and we were all doing drugs and you know, all, all drinking, bro.’

He added: ‘She just did too much man.’

He also broke down during an interview with American TV host Dr. Phil as accusations were flying, crying in his mother’s arms and wailing: ‘Mom, I would never hurt anybody!’

And an incident that reportedly occurred just 24 hours before Whitney’s death in February 2012 may show that Bobbi had a history of falling asleep in bathtubs whilst intoxicated.

Police sources told TMZ that Bobbi Kristina was drinking with her mother in the bar at the Beverly Hilton Hotel the night before she died, after which she went back to her room, ran a bath, got in – and fell asleep, causing the room to flood and forcing security to stage a rescue.

‘They unlocked the [bathroom] door, found her asleep and pulled her out of the water,’ a source told the Daily Star at the time.

However, in another twist to the tale, a lawsuit filed against Nick last month claims that he was stealing cash from Bobbi Kristina’s inheritance, including $11,000 since she was put into a coma.

The lawsuit also claimed that he had been violent towards her, citing one occasion where  he dragged ‘her upstairs by her hair.’ It also claims that he punched her in the face and knocked out a front tooth.

Documents filed by Belinda Hargrove, Bobbi Kristina’s court-appointed conservator, allege that she had planned to reveal the abuse to a close friend and had set up a meeting on 31 January – the same day she was found face down in her bathtub.

But Nick – who was only allowed to visit Bobbi’s bedside once whilst she was in a coma – has maintained his innocence, telling a friend: ‘ ‘I didn’t do anything to my baby.’

He added: ‘I just hope she wakes up and tells ’em what they all need to know.

‘People are just jumping on my back cos she loves me. There’s a load of nonsense being said about us. I love her, but I can’t get anywhere near her.’

Nick is understood to have hired a team of top lawyers in the wake of the lawsuit, although no criminal charges against him have yet been filed.

So what really happened to Bobbi Kristina? Whilst the preliminary autopsy results – released yesterday – state that there is ‘no obvious underlying cause of death’ and ‘no significant injuries’, the Medical Examiner won’t make a final announcement until he has reviewed medical records to determine if drug testing after the accident was relevant.

Bobbi Kristina’s life story in pictures

Stephanie Wood