Corrected entry: SPOILER ! Heddy cleans the entire apartment to get rid of any evidence she lived there, such as fingerprints. But she didn't seem to care too much about eating and drinking in Sam's apartment right before she killed him.
Ral0618
8th Jan 2005
Correction: I'd say this is more of a character mistake then a movie mistake, as Hedy didn't go to see him with the intention of killing him, only to trick him. She cleans the apartment and dyes her hair black after the murder so anyone with a description of Sam's visitor would describe Allie.