I don't think the flirting had much to do with it, really. Kate was a laugh, rarely said a bad word about anyone, didn't conspire or bitch, and even when she flirted it was comical. Follow the van, indeed!
Mel, by comparison, appeared ruthless and calculating. And the flirting with one of the guys (was it Andy) seemed really serious, and when he left she was reported as wanting to see her again, outside, next minute she was flirting with Tom.
Kate just seemed to be having a laugh and none of it (including with Spencer) ever seemed that serious. Her favourite male in the house was Jonny and he was not available, so she just had some fun. That's how it always looked to me!
Jade is saying whatever will make her money. She rightly said that Kate's obsession with putting on weight when she is still quite slim could have a bad effect on young girls who might get anorexia. But Jade didn't say anything in the house, simply because someone probably pointed it out to her after she left! Now she says she knew this was wrong inside the house. So why did not she say something then?
Sorry, Jade, the words "sour" and "grapes" spring to mind...