I found the storyline to be quite similar with a real case of Gypsy and Deedee. The motive was different, but the way the mom convinced her child that she was sick was probably similar. Maybe the writer was inspired by this case.
It's true that it's predictable after 30 minutes of watching, but it's still interesting to watch. You'd still want to continue watching to know the ending. The ending itself was satisfying for me. I love plot twist! Added by the great acting quality of both main actresses, suitable music scores, and right duration, it's worth to watch.