The girls, who are part of the cast for MTV's new Welsh reality show, admitted that there was "a lot of tension" between them when they first met.
"We all don't get on at the start, there's a lot of tension," Harris told Digital Spy. "Towards the end we all gel a little bit.
"But there's a lot of arguments, and bitching, backstabbing."
Asked why they didn't initially get along, Belmonte said that she wasn't happy about being stuck "with a bunch of princesses", but the arrival of tomboy Belmonte helped her cope.
"There's me coming in swinging my balls around," the 23-year-old reminisced.
Meanwhile, law student-turned-model Jonathan said she had trouble forming a first impression of Belmonte because she had "seen [her] boobs before her face".
The Valleys begins tomorrow (September 25) at 10pm on MTV.