I extremely enjoyed this movie. It all starts with the actresses playing and executing their roles perfectly. The plot is easy to figure out, but the intensity and execution were enough to keep me entertained till the end. Just keep an eye on all the details, and the mom's motivation becomes clear as crystal. You get a taste of it at the beginning. It is not something any mother wishes upon her own child.
Spoiler:
The ending is what threw me for a loop. Chloe never cared about her "mom" at the end. She visited to exact revenge. She gave her "mom" pills to keep her in a somewhat braindead state, while Chloe talked about her life.