Yes, perhaps Eliza should/could have been more careful and sensible but she was a 16-year-old girl being seduced by a far more experienced man, who probably told her that she was the most beautiful woman he had ever seen, that he truly loved her and wanted to marry her...etc, and Eliza, as a naive, innocent young girl, most likely believed this and thought that he really did love her. If you were 16, naive, innocent and trusting, and a handsome, dashing man told you that he ardently loved you and wanted to cherish you forever, wouldn't you be swayed towards him?

Many 16-year-olds would not have allowed Willoughby to seduce them, I cannot imagine Elizabeth Bennet or Fanny Price allowing themselves to be seduced (their minds, sense and intuition would likely prevent them) but Eliza evidently did not have a strong mind or enough knowledge about the world to know that allowing herself to be seduced by Willoughby was a bad thing. As I said before, I think that blaming Eliza is unfair, and it is the same as blaming Tess in Tess of the d'Urbervilles for her misfortune, which many people of that era would have done - "Oh, fickle woman, she brought it upon herself” etc etc and all that nonsense.

Willoughby is evidently a practiced charm merchant; he deceives both Marianne, the other characters and the first-time reader with his dashing ways and handsome looks, but he is not to be trusted. If Marianne had not been the daughter of a gentlemen, albeit somewhat fallen from society, and did not have the protection of a caring family, Willoughby would probably have tried to seduce her in the same way as Eliza.

I am currently taking part in an Oxford University online Jane Austen course and in one of my recent posts there, I spoke about the ways in which one can begin to feel sorry for Willoughby, especially during chapter 44 when he appears genuine, but I have no pity for Willoughby and if I do find myself softening towards him, as Elinor does in chapter 44, I think of Eliza and do not find it at all difficult to harden my "heart anew against any compassion for him" (Ch. 44).

As Emily Auerbach says in "Searching For Jane Austen", "John Willoughby [is] an idle, dissipated, extravagant 'gentleman' who marries for money and seduces for pleasure, leaving broken hearts and lives in his wake" - I completely agree with her viewpoint.