Please check if this sentence is correct:
She fell sick for two days (thursday and friday) in the last week. Due to the bad health condition she could not come to school on these days.
She was ill Thursday and Friday last week and could not go to school.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.