It sounds like one of the Paranormal Activity movies, but as I've seen the first three I can say for sure that it's not one of those. It could, however, be Paranormal Activity 4 (2012). I haven't seen it yet, but the movie style and the synopsis definitely fits your description.
It has been five years since the disappearance of Katie and Hunter, and a suburban family witness strange events in their neighborhood when a woman and a mysterious child move in.
It was released last fall, so it could definitely have been the movie you saw a few months back, and it also features a teenage girl who, I'd say, is very likely to survive for almost the entire movie ;)