As some one who struggles with a hearty handful of mental disorders that include seasonal depression... I had a hard time watching this movie without getting anxiety and closure. I watched the whole movie through and I disagree that depression and self-image can change that quickly.
If you are someone who is easily impressionable, and has a hard time with any emotional/ mental disorder, I would watch at your own risk. It has many triggers for anxiety and panic attacks.
On the other hand, I will say it is a fairly good movie. Dark humor, with a very adult approach to the world. However, still childish considering the outlets she took to escape her reality. Not everyone is who they seem to be, and you can learn from that.