Kristen Stewart 'fretting' over red carpet appearance... as Robert Pattinson's sisters warn him not to take her back

Kristen Stewart is reportedly 'fretting' as she prepares to face the press in her first public appearance since her split from Robert Pattinson.

The actress has kept out of the public eye since her affair with director Rupert Sanders became public knowledge more than a month ago.

While she has been seen nipping to the gym, she has yet to make an official performance, cancelling those planned before the scandal.

But all that is set to change with the premiere of her film  On The Road at the Toronto Film Festival on September 6.

Going it alone: Kristen Stewart is dreading her next premiere at the Toronto Film Festival this month; seen here at the premiere of Snow White And The Huntsmen

Kristen is contractually obliged to be there, but is reportedly overcome with nerves about the prospect.

'Kristen Stewart hasn’t been able to get a wink of sleep in the run-up to the film festival,' a source told Radar online.

'She’s been fretting over the film’s premiere.'

Members of the media have been banned from asking questions about Kristen's personal life, but she is said to be worried that the affair will colour the film's reception.

'Kristen’s worried that because it opens the festival, a lot is expected of it and just prays that it’s well received,' the source added.

Don't take her back! Robert's sisters Lizzy and Victoria have told him he can't trust Kristen ever again

Following her promotional obligations for On The Road, Kristen has an even bigger hurdle to overcome.

She will be busy promoting the new Twilight film, Breaking Dawn: Part Two, along with her estranged former lover Robert.

Since the 22-year-old's affair with Snow White And The Huntsmen director Sanders her former boyfriend has moved out of the home they shared, which is now up for sale.

He has not talked about his Twilight co-star's betrayal.

But according to a new report his siblings, Lizzy and Victoria Pattinson, have warned him against getting back with his ex-girlfriend, saying she's liable to do it again.

A source told Radar: 'They will kill him if he gets back with Kristen.

'Lizzy and Victoria feel terrible for heartbroken Robert, especially because of the embarrassment that was caused by the manner in which the affair was exposed.

'It's a case of once she's cheated, what's to stop her doing it again?

'And Lizzy and Victoria are pretty unforgiving over Kristen's actions.'

The protective sisters are instead recommending the heartthrob throws himself into his work and a bachelor lifestyle.

The source added: 'They believe Robert should embrace singledom, throw himself into work and not consider settling down with anyone until he's ready.'