Poor Lucy Gault feels her whole life like she orphaned herself. Without any explanation from her parents, she wrongly believes that when they were trying to move, that they left her behind. They actually believed she was dead, but in any case, it's no one's fault except the IRA driving their family back to Britain (they are British loyalists during the Irish War of Independence). The truth is that Lucy's experience of loneliness is extreme not because she is particularly evil, but just by fate.
This makes her into a religious martyr for loneliness, in a way. As an orphan, she represents the true cost of conflict like the fighting between the IRA and the British army. The true cost of war is absolute suffering, and war makes a lot of orphans, so the metaphor is apt.
Lucy wants love more than anything else, but not just any love will do. She realizes that even when she wants to connect with someone, she simply can't figure out how to be open or vulnerable, having been neglected in those ways by her life of loneliness. Her experience of loneliness has become severe and self-perpetuating, because without experience to go off of, her experience of intimacy is traumatic. The loneliness is traumatic, and the human contact is traumatic. She is perplexed.
When she finally reconnects with her dad, she discovers that he ended up in the same emotional trials for many of the same reasons. Her peace will depend on her ability to afford herself forgiveness and love, because what she wanted from her father is simply not available to her from him, but self-love could afford it. The right answer would have been to offer herself unconditional self-love, but the implication from the final image is that she disconnects from her life instead.
