Personally I don't like to be helped unless I ask. There is nothing more frustrating than someone telling me to 'slow down' or 'breathe' or try to guess which word I'm trying to use which just makes the whole process more drawn out. My other half just pays no notice and lets me get on with it, she knows the drill, but I also think she doesn't notice when I do it anymore because sometimes she'll comment that I haven't stuttered lately despite doing it about 3 minutes before.