The duo will square up against Luke Anderson and Deana Uppal this evening and one housemate will be axed via public vote.
Rebecca is the favourite currently to get the chop, with odds of 8/13 at Paddy Power. Ashleigh can be backed at 6/5.
Luke A is the outsider with odds of 12/1 to leave, while Deana is the long shot, rated at 33/1 to exit the show this evening.
There is the possibility that a second housemate could be evicted tonight, with 'White Room' task finalists Luke Scrase and Conor McIntyre being offered £50,000 - half the show's prize money - to leave the compound for good.
Big Brother airs tonight at 9pm on Channel 5.
[Big Brother Day 59 - In Pictures]
Copyright: Channel 5