There are way too many flashbacks in this film. It was really annoying. I think there were more flashbacks and dreams than there were present moments.
She made so many survival mistakes but I don't blame her because her character is not someone who have had any training or experience in the woods, so it's believable that she would make mistakes, such as sticking around an area where a grizzly visits, burying Sam but not salvaging his clothes for survival usage, tossing away useful cordage like her dental floss and the lighter, etc. It's believable that she would make these mistakes so that's a good point for the movie.
What's bad are the things the writer expects us to believe. Here are a few examples. We are expected to believe that she was able to keep the fire burning all night and day with just a few twigs. There was no evidence of any pile of collected firewood. You need piles of wood to keep a fire going. Also I don't believe for a second that a beefy watch like the one Sam had would have a magnetic clasp. Magnetic claps are the weakest kind of clasp you can have for a watch. A beefy watch like that is going to be secured with a solid clasp. Furthermore, there is no way she walks after a boulder like that lands on her from a 10 feet drop. She drops multiple times like that and only suffers a sprain ankle? There are so many unbelievable moments that combined makes it difficult to take the film seriously.