Ballaragh is in Lonan - Abbey lands I think;
Boalley Voar could be Bwoallee 'Moar '(fold large - M goes to V in fem or genitive) which could be a field name;

Re significance of being an heiress - surely the manx genes havn't dissipated that much - 'land,'land' and 'land' were the key things for much of the time - land could feed you, act as security for bad times etc - an heiress brought with her a significant dowry in terms of the land, often you see arranged marriages to ensure land stays within close family. Unlike America land (esp good land) was in short supply.