It isn't even the fact that Sharron ignored Chris and Jayne's advice (although I think she's an idiot for that; they're not infallible but they're still incredible skaters and performers, which she most definitely is not) but by changing the song without consulting with anyone on DOI as she seems to have done, she presumably didn't take into account the fact that costumes and lighting will have to have been changed, the running order may have needed to be changed and possibly some other people's music might also have needed to be changed mid-week in order accommodate the change in hers. Plus ITV will have needed to get the rights to use the music she chose. It's not so simple to change the music just because you don't like what you've been given; there's loads of other factors that need to be taken into account.