I had same experiece. My daughter had only been left with her father and my mother, prior to her starting pre-school at 2 1/2. She screamed and cried all the time she was there (two sessions per week) but I was told they had never had a child who didn't settle. After two weeks they told me to take her away and try again when she was a little older as they felt she wasn't ready. She went back when she was 3 and settled in straight away. By then though, the pre-school had moved premises so it was like going to a different place to her. I wonder if your daughter going back to the same place brought back her upsetting feelings? Can you try a different pre-school? If she still doesn't settle, it might also be worth asking if you can stay for a short time each session and gradually reduce the time until you can leave her happily in their care?
Having settled well into pre-school, we then had the same problem when she started school so be prepared!
