wtf at the ending SPOILERS

that pissed me off. that lady went through so much hell. I was assuming that after all that crap, that she'd have a happy ending. and how the hell did the evil mom survive? and also one of the brothers. there was 4 right? I saw 4 of them die. who the hell was that man in the car with them? and why did the daughter still help them? I thought she was better than her family and would turn on them. in the final battle in the kitchen, I honestly thought that when the evil mom was trying to stab the lady with that meat thermometer or whatever, that the daughter was suddenly show up from behind and knife her mom through the throat or something. damnit. this movie pissed me off all the way through and then even the ending was bad. I hate when watching a movie puts me in a bad mood. now I need to find something to cleanse the crap of this film out of my mind