This writeup refers to Books and Line numbers in Richmond Lattimore's verse translation.

Starting with lines 390 of book 3, Aphrodite appears to Helen after she rescues Paris from the battle with Menelaos. However, Aphrodite disguises herself. It seems as though Aphrodite has given Helen to Paris in return for his judgement against her will, but I can't picture Aphrodite dragging Helen to Troy kicking and screaming, it seems as thought she "beguiled" her into leaving her family in Troy. Although I do think that Helen loves Paris now.

I have a theory about this. I think that when mortals are in the presence of gods/goddesses, they are affected by them emotionally or psychologically, each according to the deity's special area of expertise. When Aphrodite rescues Paris, she places him in his bedchamber (3: 383) and he seems to be eager for Helen to join him there (I'm trying to be delicate here). I think part of his eagerness comes from just being in the presence of Aphrodite, she seems to exude sensuality that bleeds into the hearts of the mortals that she comes in contact with, I'd be interested to know if her wiles affect her fellow Olympians in the same way. This may explain how her bribe to win the Golden Apple worked so well on Paris to begin with, not to mention how Helen was persauded to follow Paris to Troy.

Now, why it works repeatedly on Paris and not so well on Helen could depend on how Aphrodite's charms beguile the sexes differently. Very often we read about beautiful women becoming adversaries. What once may have been flattering (who doesn't want to be thought of "The Face that Launched a Thousand Ships") may now be dreadful. I think Helen may either see through Aphrodite's charms (much like the disguise) or may have just tired of the romantic idea of it all now that she sees the carnage that she has caused going on for so long.