Awww.... sorry for your loss and love the pics of your new girl with Elsa. I've actually had a lot of luck introducing sows to a new friend. We had a similar situation where we started out with a same age pair, but one of them passed away around 18 months following a nasty dental infection and we didn't want our remaining pig to be alone for the rest of her life. Thus far we have had Linney and Frenzy, Linney and Sundae, Sundae and Hadley, and Hadley and Leela and each pairing has been unique, but they have all gotten along well and appreciated the company. Ironically, the most contentious pair we ever had was our initial pair of Linney and Frenzy (Linney was kind of hard to get along with.) Our other pairs have all been smoother.