The presenter said that although she believes the contestants "genuinely" care for each other, they'll feel less of a need for companionship in the real world.
"I think they genuinely like each other but I don't really think it will last," she told OK.
"I think they have been thrown into a situation where they have a companion, security and it's nice to have that in there - you need that feeling."
Ashleigh herself has been having doubts about her romance with Luke, pointing out to him recently that they aren't compatible.
"I'm messy, you're tidy, I click my fingers, you hate that," she said. "You make me feel really insecure... in everything you do."
Ashleigh admitted to having a crush on the nightclub promoter after less than a week in the house.
Big Brother continues daily on Channel 5.