My older dd, mostly home educated, went to school for a term in Year 5.
In the main, she did not like it. There were things she liked and things she didn't like.
She was never distressed at having to go.
When she didn't want to go, it was because there were other things she would rather be doing and she didn't want to have her day mapped out in detail for her by someone else.
I guess her experience was probably not relevant to your little one, because my dd was so much older therefore self-aware. She was able to explain pretty clearly how things were for her, so I wasn't left guessing how bad it was or what the real problem was.
Looking back on it, I think this may have been part of the reason why I was so unkeen on sending her to school at four but entirely relaxed about her going when she was older. When they are little, it's really hard to know whether they are OK with school, how OK they are, and if they aren't OK then why they aren't.
My mum, for example, thought I was fine at school because I stopped running away from school after the first few days and there were some things I liked about school. But I remember the dread of school dominating much of my life until I was nine, and it was never a place I wanted to be. I guess it didn't show much, and perhaps people thought I was a naturally anxious child rather than seeing that I disliked school.
Hope you figure out what's going on with your little girl and that you are able to make things better for her!!