I think overall this was well written and acted. I have known people like Mercy in my own life, one woman in particular who I have never forgotten. To be the person on the receiving end of such a roller coaster is agonizing. You keep hoping things will get better and they don't. At some point you realize you can't save them and have to make a decision that hurts both of you just so that you don't die with them. It's a choice nobody should have to make once they love someone in a committed relationship. As the other partner in the relationship you sometimes find yourself wondering if that person does get themselves together and moves on then was your decision to break up with them not the right one. You ask yourself whether you were not patient enough, tolerant enough, or whether you may have contributed in some way to the bad outcome, but then who can really know for sure how much is the other person and how much is how you related to them. That's nearly impossible to determine.
This thought process brings me to the ending of this story when Mercy's former girlfriend met with her for closure and when Mercy tried to get her to come back she said "I can't. You're toxic." Alcoholics will say a thousand times they've gotten it together so from her perspective I can see why she would not want to take the risk, but I have also known alcoholics who have been sober for 20 years; so I question whether to call her "toxic" is an accurate statement, and perhaps too harsh and too absolute. Mercy's mother was obviously toxic, but in many ways Mercy was a victim. She did not seem narcissistic, just lacking in direction and sort of drifting through life without a plan. One gets the sense that she is going through the motions of living and probably underneath it all is going through serious depression which has not been addressed. She goes to AA but has no sponsor, and does not seem to be in therapy. Until the depression is addressed she probably won't be effective in her life. It doesn't seem as though she's a manipulator, exploitative, nor intentionally cruel to those around her; just someone living a subsistence life (which I think was the case of the person in my life who was the same way).
In some places the story seemed a little disjointed. Who was the man she borrowed money from who was being so glib and making her wait while he addressed envelopes. He seemed to be some sort of a friend of the family, but that could have been filled in a little more. I'm a writer so I notice things like this.
I would have liked for the story to have followed her a little further. Other than that I think it was an excellent movie. The long pauses between her responses in conversation was a nice touch to show how hard it was for her to express herself and punctuated the gravity of her life.