I watched the movie on Netflix about a loner guy who spent much of his time looking out the window of his apartment and crushing on one of his neighbors.  She was odd herself and something about a gift that she wore in her hair or perhaps made a dress out of.  Anyway, they start dating and doing things together.  I recall the twist was that she was a killer and when he finally visited her apartment she had either killed someone or planned to kill him.  Sorry, I don’t recall more, but I do remember that I enjoyed the movie and would like to watch it again, just can’t remember the name.