Great acting! BUT the premise is complete shit. I see why it has pretty bad reviews so far. Unfortunate that they couldn't have had a slightly altered ending.
SPOILER AHEAD :
The lunatic villain should not have won. In a movie called mothers' instinct, why the hell did the mother who actually had the good instincts about the lunatic, Get killed in the end only for her son to be adopted by the lunatic?!? Garbage.