Complex sentence: Tristan tells Liz that he loves her, but she refuses his advances on behalf of the Countess and their relationship, with Liz informing him that she thinks she loves him too, but doesn't want to tell the countess yet.
Split into simpler sentences: Tristan tells Liz that he loves her, but she refuses his advances because of her relationship with the Countess. Liz informs him that she thinks she loves him too, but doesn't want to tell the countess yet.