“Why — how could I love him — possibly?”
This is different than saying “I never loved him.” Daisy is confused because it makes no sense for her to love a man who cheats on her and possibly beats her, but somehow she still loves him.
This scene paralells the part of Tom and Myrtle’s party where Myrtle is asked if she loved Mr. Wilson. Myrtle has no problem selling out Wilson to show off for Tom, but Daisy can’t bring herself to do the same to be with Gatsby.
To help improve the meaning of these lyrics, visit "The Great Gatsby (Chapter VII)" by F. Scott Fitzgerald and leave a comment on the lyrics box