One thing I was disappointed they didn't include
I wish they had developed the character of the Vicar more as I loved him in the book. I loved the part in the book where she goes to him when she's feeling so lost.
I also think they didn't spend long enough on Cassie being so terribly in love. She spends quite a long time in the book wondering around, trying to deal with her feelings for Simon. In my opinion, that was the most magical part of the book, when it's summer and she is spending a lot of time in solitude. It's seems quite an important bit.