The 36-year-old - who recently finished fourth in this year's series of Dancing On Ice - makes her comeback in the summer for a handful of episodes.
Little is known about the circumstances surrounding Sam's reappearance in Walford, other than that she is released from prison harbouring grudges and "a big secret".
It is thought her return will coincide with Barbara Windsor's departure as Peggy Mitchell, after 15 years in the role.
Executive producer Bryan Kirkwood this afternoon told Digital Spy: "When Sam Mitchell is in Albert Square, trouble is never far behind. We last saw her heading for a stretch in prison and ostracised by her family. When she returns on her release, it's with a lot of grudges and a big secret."
He continued: "Danniella brings a lot of fun and mischief to the role of Sam and I'm looking forward to having her back where she belongs."
Westbrook reprised her role as Sam in April last year. On screen, the Mitchells attempted to hide her from the police but the law quickly caught up with her when she was arrested for trying to flee the country again.
While rekindling her romance with Ricky, Sam also had an affair with Jack Branning. She then became embroiled with Archie, who convinced her to skip bail and ultimately cause the Mitchells to lose The Vic.
She made a surprise return on Christmas Day ahead of Archie's murder and quickly became a suspect. However, on hearing her mother Peggy and brother Phil's plan to use her as a scapegoat, Sam turned herself in to the police.
In a final showdown with her mother, Sam rejected her mother and made it clear that she had no interest in the Mitchell name.