Troubled Demi Lovato was reportedly 'a mess' during her relationship with Jonas Brothers star.
An insider told Twilightstar Ashley Greene caused Demi to compare herself to the actress, who plays Alice Cullen in the vampire flicks.
Following rumours that Demi was 'gunning' for Ashley during the Jonas Brothers tour, allegations have now suggested that she became 'insecure' of her own body image, especially in relation to Greene.
A tour source told the mag: "She compared herself to Ashley. Measuring her weight, her height, her hair. She was obsessing."
It is thought that all of these issues contributed to her stint in rehab, but Demi's 'fight' with backing dancer Alex Welch has been described as the 'catalyst' of her breakdown.
According to US Weekly, after her split with Jonas, Demi's step-father and manager warned her they felt she was partying too hard, with Lovato thinking that Welch had tipped them off about her behaviour.
A source then claims the 18-year old attacked the dancer on a plane departing from Peru, stating that Demi: "Walked onto the plane, did not look at the girl, then suddenly punched her in the face and threatened her with a slew of expletives."
They added: "Demi’s manager asked her, ‘Are you in control at all?’ She said, ‘Sorry, I just lost it.' It was the last straw…" before claiming that it was Demi's decision to admit herself to rehab to seek help.