Hi, Amy,
Sorry to hear about your problem with your dog eating its faeces. Not a pretty sight, and it clearly upsets you more than it does her!
The first thing to do is to get her throroughly checked out by your vet. The problem may be that there is something wrong with her physically. If not, you have a behavioural problem to cope with, which may well in fact be easier to deal with.
The best advice I can offer is to get her into a routine - always take her out straight after a meal, remove the faeces immediately so that she does not get access to them. Never leave them lying in your garden - take her out on a lead and pull her away if she makes any attempt to turm to consume her motions. As soon as she has defaecated distract her attention with a tidbit of something that she likes - reward is alway better than punishment in cases like this. If you have been punishing her or chastising her she may have associated it with the passing of faeces, and not the eating of them, so she tries to remove th evidence!