Julia Koch – the second-richest woman in America — may not be on the social scene, but she is keeping busy. We hear the famously private socialite has been creating a family compound in the Hamptons, complete with multi-million dollar renovations. Koch, who is worth an estimated $81.2 billion, owns two homes on Meadow Lane in Southampton, also known as “Billionaire’s Lane.” She quietly scooped up another nearby plot for $33.5 million in the past year, we hear. A source revealed she is creating a “family compound,” for her three children with late husband David, who passed at age 75 on August 23, 2019. We hear Koch has been busy updating…