The Buccaneers uses their score so masterfully! When Lizzy is hiding what happened with Seadown, we hear a short part of Nan's Theme. But it's muffled and dark.
When Nan finds Lizzy's earring in Tintagel, we hear that same leitmotif, but it's loud and overwhelming.
The use of Nan's Theme in that second scene indicates how pivotal this scene is for Nan and Lizzy's relationship, and the connection to the first use of this particular leitmotif already foreshadowed how bad the fallout would be (even if Nan's honest reaction without the pregnancy would not have been that bad at all).
What I also find fascinating is that the show uses the vocals of that leitmotif for one of the S2 scores called Affairs (which I will do another post on). We hear it when Theo shows up at Hector's auction, when Theo and Lizzy kiss for the first time, when Nan unexpectedly shows up at Theo's art studio, and when Nan finds out that the earring she found was Lizzy. The use of those vocals ties Nan to Theo and Lizzy's story.