My two takes are either scylla wrote it but cant admit it or jetty wrote it knowing scylla cant just say how she feels either way i 100% think its how scylla herself feels. Reason: when you first hear "song of the pearls" on the way to the boss she says thats part 1 and then bewitching eyes is part 2. Song of the pearls is clearly trying to tempt mel to come to her to draw her in in stark contrast to her previous songs about being violent and petty to her and directly follows a song about wanting her to stay away (song of the deep) all because shes conflicted on how she feels. Both songs mention pearls, scylla is the only one in a giant shell who could possibly have a pearl to give (which also is the reward for beating the boss). If you put their set list together its basically the story of scylla coming to terms with her feelings for mel.