Take her dummy away, I think I saw some of her piccies in the photo gallery of her with a dummy didn't I? You need to be her dummy. Instead of her getting sucking comfort elsewhere, it needs to be you. Every single time she wants to suck, it should be boob.
I remember when my LC asked about dummies she said if you have to have one make sure it's the round type not the nuk type because the shape of the nuk dummies is exactly the shape you are trying to avoid with BF... I have no idea what you are using but just wanted to add that (even tho it's not what Shannon was talking about ).