Though Victor cannot stand Sibyl, how does his behavior reflect on one of the themes of the play (about private lives)?

Victor helps Sibyl because he believes it is the proper thing to do. He comforts her when she cries and even defends her to Elyot, denouncing him for causing Sibyl so much pain. The reality of this situation, though, is that Victor finds Sibyl to be incredibly annoying and has barely tolerated her throughout their journey together. However, he kept those opinions to himself and acted as he believed he ought to in a public situation. Had he acted on his impulses, Victor may have left Sibyl behind and looked for Amanda on his own.