Skip to 18:30 for the start of the incident, 27:40 for the host threatening to eject the bullies, and 39:05 for Kayleigh quitting the game:
For some background context, Kayleigh kissed one of the guys off camera (Bananas) in the first few days, but after that Bananas grew really close to Natalie (from BB18 US) and Kayleigh grew close to a guy called Nelson. But it only just got revealed to the rest of the house that Kayleigh and Bananas hooked up one time (which was before Natalie was even speaking to Bananas), so 3 girls who had nothing to do with the situation decided that Natalie has a right not to have to share a room with Kayleigh, so they grabbed all her suitcases and personal items and threw them from the top floor to the bottom floor. They also tried to prevent her from sitting with them in clubs and tried to get the rest of the house to ostracise her as well. After spending the night in a hotel, Kayleigh returned but quit the game at the end of the episode as it was causing her anxiety to have to live with the bullies. The host warned the bullies that if they ever did anything like that again they'd be ejected from the show. He also hinted that Kayleigh will be invited back for a future season.
I actually feel really bad for Kayleigh. I mean, yeah it is karma for the way she behaved in the BB house, but still it was really difficult to watch, especially since I've been watching the whole season and she's been quite lovely and humorous actually and nowhere near as nasty as he has been on the UK shows. Those girls are honestly trash and they're all over Twitter saying how 'they weren't bullies but if they were then I claim Regina George' etc. and it's all a bit pathetic really.
Another Ex on the Beach girl (Melissa) was treated pretty badly on the show as well but she stood her ground alot more than Kayleigh did until she was eventually eliminated, and it wasn't near as bad as this level of treatment.