Up to midpoint in the book, Eliza is juggling Boyer and Sanford, saying neither yea nor nay to either of them. When we hit midway, Boyer is actually the one who leaves Eliza, as he is tired of having his emotions trifled with and he believes she prefers Sanford over him as he saw them ‘cavorting’ in the garden. From then on what happens is all guesswork. From hints given us by Hannah, it’s suspected that Eliza will pursue a relationship with Sanford since Boyer is essentially out of the picture. However, we know that Sanford’s motives aren’t pure, as he needs a rich wife and Eliza sadly doesn‘t fit that part of the bill. So even though he claims to love Eliza, we know Sanford won’t marry her because he values material things above trivial things such as love and emotions. So if she does pursue a relationship with him, it’s doomed to failure, which would therefore leave her heartbroken and in despair. Maybe this will be the real reason she dies in the end--because she has no will to live.