Why is my 9 month puppy STILL eating her own poo plus other dogs when we walk?

When she does it (or tries to), pull her away and shout "AA AA AAAH!" or something that would sound equally alarming. Make her realise she's done something wrong. Hopefully she'll learn that something unpleasant will happen when she does it. When she chooses not to do it, then reward her - tell her she's a good girl and give her a treat. You need to somehow drill it into her head that it's a bad thing to do. She's a dog, her nature is to please you, so make sure she's made a fuss of when she doesn't do it :)