The House Sitter.

A family still reeling after the accidental death of one of their daughters, returns home after an aborted month long getaway to Rebecca, a seemingly pleasant house sitter. Since they returned early, Rebecca has nowhere to go, so the family invite her to stay. At first, Rebecca is a godsend—she cooks, cleans, and does laundry; but the family soon discovers that the woman is not as innocent and sane as she appears.