This is very normal, after school holidays they will feel sad to go to school. My 6 years old still behave like this because she misses parents and sibling at home.
My daugther also claimed that teacher in school is very fierce and she scared teacher scolding her. But after I tried to ask more details from my girl I realise actually it was teacher scolding other students and she is afraid. I tried to explain to her why the teacher is fierce and scolding (class got class rules etc.).
It is perfectly fine for you to check with the teacher on what is going on. I don't think this will offence her since your tone is just checking instead of accusing. I always chat to teacher to understand more on what is going on with my daugther in school.
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