One thing to consider is the murderer could have washed her off after the crime itself.. Yes, the perp could have, but I would have expected to find more hairs in DW's sink trap (assuming he is the perp) if he had washed her off.
Hi Mrs L.. yes I agree...maybe she was washed elsewhere but I have no clue as to where or how. It seems more logical that he washed her hairs off of him.
Will be back after lunch..