Upon hearing of the death of her sister's husband, the Duke of Cornwall, Goneril says, "One way I like this well," but we're never told what that "one way" is.
In contrast, Goneril immediately says why she dislikes the news that her sister's husband is dead. Goneril is having a love affair with Edmund, Gloucester's bastard son, who she just sent back to take charge of Cornwall's armies. She says that her sister, "being widow, and my Gloucester [Edmund] with her" may steal Edmund's affection from her.
But why should she like the news that Cornwall is dead? It might be supposed that Goneril thinks that with her brother-in-law, Cornwall, dead, she might be able to seize the other half of realm from her widowed sister, Regan. Politicians do such things. But this a mere supposition, and the subject is never mentioned again.