Pallett, 35, said the former Coronation Street actor hurt her.
Roxanne's exit makes her the second housemate to leave without eviction this series following Rodrigo Alves' removal for "serious inappropriate behaviour".
Big Brother said in a tweet this morning: "Roxanne has made a decision to leave the Big Brother house".
"She has now been reunited with her fiancé and family and thanks everyone for their support during her time in the show".
The allegations have sparked over 11,000 Ofcom complaints and thousands taking to Twitter to claim Pallett invented the allegation in an attempt to get Thomas evicted - who is now the bookies favourite to win the series.
Thomas, 34, said there was no "malice" in his actions, with some viewers arguing that the incident was only play-fighting.
The actress initially appeared to take the incident as a joke as she playfully referred to Thomas as a "woman beater".
He said: "I want you to know from the bottom of my heart I was showing my affection".
'I don't know what I've done, ' Roxanne said.
Dan Osborne concurred, saying: 'He has just admitted he's had a problem with her from years ago, and to me you don't hit someone like that if you don't like them.
Sally took the opportunity to be brutally honest with the actress, as she told her: 'I think people just think that you spent the night in [the separate room] because of what happened, and you still stayed.
When he was asked further about how he feels about Pallett, Jardine said: "All I'll say is she's a lovely girl, she does what she does". I'm looking at the little lady next to me.
Celebrity Big Brother continues on Channel 5.