In the hour-long festive special, Becky, played by Katherine Kelly, drowns her sorrows after discovering that her ex-husband Steve (Simon Gregson) has proposed to Tracy Barlow (Kate Ford).
She sets fire to photos of Steve but subsequently falls asleep, causing her flat to go up in flames, according to the Sunday Mirror.
Gregson and Kelly were spotted filming emotional scenes in Manchester last month, which were rumoured to include the moment Steve makes his final choice to stay with pregnant Tracy.
Kelly announced her departure from Coronation Street in April and her character will be seen for the final time early next year.
The latest reports suggest that Becky will ruin Steve and Tracy's wedding after she is falsely accused of killing Tracy's unborn twins by pushing her down a set of stairs.