Lady Louise has “fallen in love” as she sets her sights on pursuing a career in the army, according to a source. The young royal is currently studying at St Andrews University, the same institution Prince William and Princess Kate attended as students. Lady Louise, 20, is a member of the St Andrews University Officers’ Training Corps. The daughter of the Duke and Duchess of Edinburgh is keen to serve her country and King Charles, according to an insider. The source told The Sun: “She talks about being very keen on a career in the military, serving the King and country. “She is all about the Ar…