Well...nobody started out being a bad person. George did loved her and she did try to be a wife to him in the begining. However the Greek Royal Family was not kind to her, they deliberately sproke Greek when they all meet up togather when Elisabetta was present. Even Queen Marie of Romania complained that Queen Sophie was tight with her jewelry (Sitta recieved a lovely Greek Scroll tiara bought from the cash scrap Grand Duchess Kyrill. That piece is still in the family and worn by Princess Margarita, King Michael). "She didn't even let me see them (the jewels)." Elisabetha did recieved some emeralds (not from Sophie) when Queen Olga died and George as King legally inherited them. She used those to make a tiara (which she later sold to King Paul & Queen Frederica).
Yes there is indeed bad blood between Elisabetta & Sitta and once she even slapped her. However when King Michael was reinstated, Elisabetha had to eat humble pie and begged Helen for forgiveness, which the nice Queen Mother did. Although by that time nobody trust ed at that point.