What do you show her as - a traditional coloured cob or a show cob? I'm asking because the turnout is totally different. If you're showing as a traditional coloured then you've got a problem because they should be shown with a full mane, long tail and full feather - I guess the best you could do is tidy it up as best you can but accept that you're going to lose marks, plaiting would be completely wrong. If however you're going in a show cob class then get the clippers out because you hog, take off all feather and trim the tail so it's about an inch below the hock when moving.
If you do some google searches you should get loads of pics of how different types are shown, and also rider/handler turnout.
