Demi Lovato struggled with intense demands, presence of ex's new girl on Jonas Brothers tour

Although the complete reasons behind Sonny With a Chance star Demi Lovato's sudden trip to rehab are not known, a picture is emerging of a young girl experiencing some concurrently stressful situations when she had a "meltdown" at an airport in Peru.

In addition to lashing out at a backup dancer, Lovato is said to have targeted ex-boyfriend Joe Jonas's new girlfriend Ashley Greene. E! quotes a "source" as saying the incident prompted Demi's departure from the tour:

"She just lost it right at the airport in front of everyone," says the source. "The [Jonases'] dad basically said right there, 'That's it. You're going home.' "

Demi also made verbal threats to Joe's new squeeze, Ashley Greene, who was at the airport as well and witnessed her meltdown, the source says.

Another source who is said to have had insider information on the tour said the combined stress of promoting Camp Rock 2 and being exposed to Jonas's new relationship constantly took a toll on Lovato:

After she split with Joe, it was just a whole bunch of drama, very awkward. Everyone tried to be professional, but you could tell it was wearing down Demi. It was a taboo subject to bring up, but clearly she wasn't over Joe.

"The [Jonas] boys got a break after the tour, but Demi went a nonstop promo campaign for Camp Rock 2 and was pushing the single for that movie. It really was too much ask of a girl that young. She just couldn't handle it."

It is not known how long Lovato is expected to remain in rehab.