Not of Midgard, Not of Asgard

People believe Loki Laufeyson is alone with nobody but his adopted brother who he can't stand. They are wrong. Loki, with all of his problems concerning family, has one person he considers his sister. Many make a connection between them as she is essentially his female duplicate. But what happens when she gets into Shield at the same time as Loki being under metaphorical lock and key?