The housemates will be reunited with friends and family as part of a new task on the show, and Bear is set to be in for a bit of a shock when Lillie walks through the door.
She had originally ruled out going into the house, with Lillie telling TOWIE star Danielle Armstrong that she "wouldn't want to see" Bear.
However, she's clearly decided otherwise and viewers will get to see her confront Bear for publicly dumping her onscreen and then moving on with his fellow housemate Chloe Khan.
Big Brother's official Twitter account confirmed Lillie's appearance, sharing a picture of her in the house. They tweeted: "12.47pm: There's a surprise visitor here to see Bear! Wonder how he'll react... #CBBLive."
Lillie had said that she wants to get answers from Bear. The pair had been dating when he entered the house, and she claims she and Bear were completely in love.
Lillie recently told The Mirror: "How can you do that to someone you care about? If the roles had been reversed, no way in a million years would I have behaved the way he has... If he doesn't want to be with me then that's fine, but why couldn't he have just said that before he went into the house?"
He, however, initially kept quiet on their relationship, only addressing Lillie after he had kissed Chloe Khan in a drunken dare.
Bear revealed he wanted to be single again and told his housemates he 'doesn't have time' for a girlfriend. While he admitted he though his relationship with Lillie would last forever, Bear then said he doesn't think she is 'the one' for him anymore.
He then went on to pursue a physical romance with Chloe Khan, and the duo had fans divided over their steamy antics on the show. Bear and Chloe have even been forced to deny they'd had sex in the house, after they were heard getting pretty intimate with each other in the toilet.
Chloe was evicted from the house last week and she revealed she and Bear are hoping to continue their relationship on the outside.
She also claimed that she had 'no idea' Bear had a girlfriend when she first kissed him, prompting Lillie to hit out at her on Twitter and question why she had then continued things with Bear once she had found out about his outside relationship.
Lillie has now said there is "no going back" for herself and Bear.
CBB continues tonight on Channel 5 at 9pm.
Follow us on Twitter @RevealMag for all your celeb, fashion and beauty news!
Fancy winning some GREAT prizes? Check out Reveal Competitions here!