I guess she didn't like seeing bare feet or something. We didn't have any hard rules about no shoes or about socks, but my sister and I usually removed our shoes before coming in the house. My sister often went barefoot, but I usually left my socks on. The only rule we had was no bare feet at the dinner table, so my sister would put socks or slippers on before dinner.
When I got to be about 16, I became very shy about my feet and rarely even took off my shoes until bed time. I secretly wished my parents had enforced a no shoes policy to force me to overcome the shyness I developed, but as long as I had the choice, I usually wore shoes. I finally got over it after a couple of years, but I was still shy about being completely barefoot around anyone but my girlfriend for a while longer. Now I rarely wear anything on my feet unless I have to.