Fiona, like Mark, is another contestant I think the producers felt would disappear a lot quicker than she has done. I originally put it down to Anton's purported fanbase, but ever since her table-trailing rumba I've been wondering how she's avoided the DO. Theories:
1) She's getting away with it by being eminently forgettable, whereas most of the other DO candidates have done something spectacularly awful to land themselves in there.
2) She's been on tied scores for a few of the weeks, which has probably helped to boost her up the points ladder a bit when voting time comes around.
3) She's managed a reasonably helpful distribution of dances. The meh waltz after the dodgy CCC, then the OK QS after the even dodgier rumba (yes, I know they scored the same, pedants

), while others have come to grief in the scheduling. Getting the dodgy paso in on the week of a bald wig and a truckload of tartan was serendipitous
4) There's still a hard core waiting for her to come good. I actually thought her tango and cha-cha were relatively promising and have been disappointed to see virtually nothing else good from her, apart from the fairly enjoyable QS. Perhaps there are a few more still holding their breath.