Ramya wrote:

"Elizabeth fell in love with Mr. Elliot, and the idea of marrying the heir of the family was too irresistible."

Did she fall in love with the man, or with his status as heir?

"She had, while a very young girl, as soon as she had known him (William Walter Elliott) to be, in the event of her having no brother, the future baronet, meant to marry him, and her father had always meant that she should. He had not been known to them as a boy;

but soon after Lady Elliot's death, Sir Walter had sought the acquaintance; ...... in one of their spring excursions to London, when Elizabeth was in her first bloom, Mr. Elliot had been forced into the introduction.

He was at that time a very young man, ..... Elizabeth found him extremely agreeable, and every plan in his favour was confirmed." (ch.1)

Elizabeth planned to marry Wm Elliott as soon as she knew he might be the heir, though she had never met him. So it is clear that his status as heir mattered first.

When they were eventually introduced she "found him extremely agreeable", which confirmed her plan to marry him. This might mean that she 'fell in love' with him, but I'm inclined to doubt whether Elizabeth really has the capacity to love anyone except herself and possibly her father.