So it sounds like it was largely a case of Sharon believing tabloid rubbish, and Dannii (in Sharon's eyes) not doing enough to put the rumours to rest? Along with initially missing Louis and wanting things back as they were... Along with the awkwardness caused by the affair, which Dannii probably doesn't want to consider as a factor..
(I know no-one probably even care any more, but I like Sharon and I don't like to think she's the kind of person to hate someone for being "prettier" than her)