Towards the end of the movie when Hannah gets inspiration from her sister, in one shot she is eating a Christmas cookie shaped like Santa. In the very next shot she is eating a Christmas cookie shaped like a red boot.
There's no such thing as Princeton Medical school. Princeton is the only Ivy League school that does not have a med school.
When Hannah is being picked up by Jake for the drive into town, she's texting with leather gloves on. Leather gloves won't work with a touch screen phone.
When the 3 are sledding Bonnie's gloves are black but when the camera angle is sledding down it has pink gloves holding onto the sled.