I don't have any suggestions for how your daughter can improve her speech, as nothing has worked on me so far. But as a parent, you can instill confidence in her and her speech and her ability to take decisions that will go a long way in helping her communicate in life. She may never achieve fluency but she doesn't have to be a social reclusive because of it. When she stutters, do not ask her to repeat it again "slowly". That is terrible for her confidence. Do not interrupt her. Do not be impatient. Do not show fake patience either. Don't bob your head too much while she speaks. Don't highlight her stutter as a life changing problem. Don't purposefully encourage her to speak out in public, be tactful regarding that. Just let her talk and as when she wants, whenever she wants like you would to normal person. Treat her like a normal person and not a special case in social situations. I don't mean to patronize or suggest that you aren't doing this already. But just my 2cents.