Your concerns are very understandable.
DAL is antagonistic because he has had a bad experience of his own, with his very gifted son not getting the stimulation he needed. And he feels this is a repetition of his own similarly unfortunate experience, which completely turned him off school.
This can happen. Then again, all sorts of other scenarios are equally possible.
I would say about half of dd's friends were reading and doing sums when they started school at 4. (Dd was not reading, but was verbally very advanced and was doing the sums and was also fully bilingual).
Our experience was different from DALs: our children had a very good time in infants and did not get bored. It must quite simply have been a good school with good teachers (ordinary state, not particularly high with Ofsted). Afaik none of dd's advanced friends have lost interest in school either.
So it's impossible to predict what your dd's experience will be like.
It is also impossible to predict how your dd will react to it. People have such different temperaments: what riles one child will be shrugged off by another.
My dd has gone through various stages where she has been well ahead, but it doesn't seem to worry her. She has found other friends who share her interests but also enjoys the friendship of girls who are not very interested in learning. I was well ahead of my class: I was not only a fluent reader but was studying two foreign languages by the time we started school at 6 (educated abroad); when English classes started I knew more than the teacher, but for some reason it never worried me. And it didn't turn me off work either. School was still a good experience and I have always enjoyed studying.
So noone can predict what is going to happen to your dd. It will depend on the school and it will depend on her.
But for the time being, I would relax and wait.