Has your daughter participated in hearing screenings at school? I would have her consulted by an audiologist/pediatric audiologist just to rule out any hearing difficulty that might contribute to her speaking loudly. Once we rule out a hearing difficulty, then we can consider an SLP to work with her on proper vocal hygiene and protecting her voice if that is needed. I would say let's rule out a hearing concern first.
When children speak loudly, it is sometimes as a result of them not hearing themselves efficiently. Have you had her hearing assessed by an audiologist or an ENT?
You might try speaking more quietly to her, and modeling that lower volume at dinner or wherever she speaks that way.
It may be a hearing or voicing issue. Have you had her hearing checked lately?