(Portland, OR)  --  A Portland woman is facing federal charges, after being accused of sex trafficking involving a three-year-old child.  Authorities say 27-year-old Kelsey Christine Wheeler was arrested last week after meeting with a Salem man, who was being investigated in connection with a child-porn case.  Investigators say he met Wheeler through a sex ad online, and Wheeler was accused of offering an "encounter" with a young child for one-thousand dollars.  Wheeler is to be arraigned on August 11th.