One Sock

A couple of days ago, I was sitting barefoot in Ella's room.  As soon as she realized my toes were bare, she pointed at my feet and said, "Socks".  So I asked her to go to my room and get me a pair.  She quickly darted off to get the socks, but ended up bringing me one sock instead of two.  I put it on one foot and showed her that the other foot still needed  a sock.  Then, I asked her to go get me another one.  She again dashed to my room, and this time, picked up a pair of socks.  I told her I only needed one. I then observed her separate the pair of socks.  She put one back in the drawer and brought me the other.