The only time I’ve heard that sort of thing (aside from Ms. JW) is with the word “fabulous” and only by gay males, or people imitating/mocking gay males.
Could be a general antipodean vocal trait. I’ve never watched the voice to know If Jessie J does do it but what I have seen of her is intensely annoying so maybe she should be sent to where her voice fits in? and yes that’s real question, or more of a plea really.