This movie has very little good to say about the nature of relationships. Nicole is a "good" girl, but she winds up trusting the wrong guy and pays a huge price for it. Margo is a "bad" girl, and she also ends up paying a price for her choices. Aside from Nicole's father, and her friend Gary, the men in this movie are violent and possessive.
The David character beats up a teen, kicking him while he's down, and slaps the Nicole character when she tries to intervene. He murders both offscreen and onscreen, sometimes with a gun, and sometimes with his bare hands (neck-snapping). He also kills the family dog and shoves the severed head through the doggie door. Aside from that, he threatens and intimidates various characters. A fight breaks out at a dance club, and various weapons are used during the climactic struggle (including a power drill to the hand, and stabbing in the back).
David and Nicole kiss passionately, and often. He touches her between her legs. They have safe sex in a bed, while her parents are out (a condom wrapper is later discovered). Margo gives a grinding lap dance to her older boyfriend. Later, a horrified Nicole witnesses as David violently seduces her best friend Margo, grabbing her buttocks, and dragging her away for implied, offscreen sex. There's also a brief same-sex kiss and a brief view of a nudie magazine.
"F--k" is used several times, and "s--t" is heard at least once. Additional words include "boobs," "slut," "bitch," and "Jesus" as an exclamation.
A friend of David's is seen smoking crack. Teen Margo smokes cigarettes, and there is some drinking.