A good subplot is so tightly woven into the main plot that it may be difficult to recognize it as a subplot with a conflict of its own. An important subplot that runs through Brontë's story is the romance between Gilbert and Eliza Millward, Vicar Millward's daughter. Gilbert takes every opportunity to flirt with and show his affections for Eliza, and she is not at all unhappy about accepting his attentions.
Miss Eliza was never in a better humour. We seemed, indeed, to be mutually pleased with each other, and managed ... a cheerful and animated though not very profound conversation.
The parents contribute to the romantic conflict. The vicar would not be unhappy with the match between the two, but Gilbert's mother would be most unhappy as she continually reminds him that shallow little rosy-cheeked Eliza is far beneath his just deserts.
When Gilbert begins to show interest in Helen, as his opinion of her starts to shift to a favorable light, of course Eliza feels the stinging slight of his neglect. This is evident when the local group makes a day trip and Helen slips away to paint the scenic view while Gilbert follows her. Eliza, whose prattling silliness is wearing and uninteresting to Gilbert, is left alone and shunned by him.
Eliza’s playful nonsense ceased to amuse me--nay, grew wearisome to my soul, and I grew weary of amusing her: I felt myself drawn by an irresistible attraction to that distant point where the fair artist sat and plied her solitary task
As Gilbert's affections shift more strongly toward Helen and away from Eliza, even her greatest feature--her eyes--begin to take on an aspect he does not quite admire: "there lurked a something that I did not like; and I wondered how I ever could have admired them ...." Eventually, as Eliza tries to help in digging out scandal about Helen, there grows an enmity between herself and Gilbert ("regard the little demon"), as Gilbert is intent upon protecting Helen's honor and on his growing affection for her. We don't learn what happens in the end to Eliza, but we do know that she is the one to give Gilbert the unwelcome news that Eliza will be married on the upcoming Thursday. Thus the split between the hero and heroine of the subplot is confirmed and the conflict resolved.
'[Y]ou had better be quick about it, I can tell you, for—alas, alas!—she’s going to be married next Thursday!’