The best advice i could give, apart from keeping her in speech therapy would be to speak a little bit slower with her. When i speak to someone who seems stressed out or is talking fast i always subconsciously mimic it and it makes me talk fast and be stressed out. I am almost completely unable to control the speed of my speech. And as you may now, stuttering gets a lot worse if you are talking fast and if you are stressed. My parents are really fast talkers and because of this i can barely talk to them at all. Hopefully she will grow out if it. Most kids do.