It is not often that I do not predict the way a movie will go. To say that I wasn't expecting the twists is to say the least. Tears were shed.
A lot of the negative reviews I've read have been about Sandra Bullock's age difference with the sister (which is clearly addressed in the movie). The second negative reviews Ive read claim that she is too monotone. It is almost like these people have never seen someone depressed and drained. Of course she is monotone for most of it, she is depressed, traumatised and clearly suffering from PTSD.
I have no idea why many of the critic ratings for this movie are so low. I absolutely would recommend this!