I would lean towards Flacka's possible reasons. The little
girl went willingly the first day or two so I would think it
had something to do with the way the classroom was being run,
or something similar. I think young children are very
intuitive and we adults should honor those gut feelings more
often then we do. My oldest walked up to the classroom door
of first grade, turned around and announced that she didn't
want to go in there. She had been in Montessori for three
years so it wasn't the thought of school that made her feel
that way. We had her visit the classroom the previous spring
thinking that would give her a positive impression of the
school where bigger kids went. She just had a feeling that
this was not going to be a good place to be. Unfortunately,
she was right and it was a horrible experience for her (and
the other children in that classroom). It set the tone for
attitude towards school for the rest of her years in school.
She was intuitive about doctors and dentists too and was
always right I would find out years later. We had to deal
with a lot of resistance about even leaving the house each
day just to go the block to school until she finally gave in
and went through the motions of going because she had to. She
never could say what it was that she didn't like about the
class except that the teacher made rude body noises and never
said excuse me. This community still allowed spanking of
students if given permission by parents and they were doing
that outside the door of the classroom with the one boy who
was terrorizing the classroom. There were all sorts of little
things that added up to a classroom that didn't "feel right"
to a little one. I am not saying that was what necessarily
was happening with the niece's child's school, but children
catch a lot of little things that adults just miss or have
grown thick skin to ignore.
Our grandchild was taken out of K after several months of
really disliking school and being forced to go. When she
changed schools the following year for first grade, there
were no issues whatsoever and she has been happy ever since.
The school she goes to is more relaxed and a lot less
stressful academically. Different children do better in
different types of settings.
I bet OP's child she is talking about will do just fine when
she goes back to school when she feels ready.