Let´s just look at her other heroines and the matches they make. Marianne Dashwood is young, well~educated, has aristocratic relatives on her mother´s side, is described as extremely handsome and has more dowry that Lizzy Bennet (though it´s still not much). Marries a wealthy man who is about twenty years her senior, out of sense of duty to her family. Elinor gets her Edward in the end, but not after he loses all his property rights to his brother and gets just enough from his mother to live on.
Catherine from Northanger Abbey comes close to being unrealistic, however, when we take into account the fact that Henry is but a second son and would probably never go so far had not his father, mistaken as to Catherine´s riches, positively insisted on him courting her, and also that Catherine is a type of a ditz head which makes men feel their inherent superiority and thus can be very attractive, it becomes more believable.
Fanny Price from Mansfield Park is a poor relative who marries her cousin, which is practically an English upper class tradition (more about it later), but not after his family realise how worthy she is. He is also only the second son.
Emma Woodhouse, the richest girl in town, marries the richest man in town, who also happens to be family, since her sister is married to his brother. Nothing to see here, move along.
Anne Elliot, the second, unloved daughter of a baronet in reduced circumstances who is nearing thirty, is finally allowed by her family to marry a naval officer who became wealthy after the war. One could say the way he kept pining for her after she had rejected him was unrealistic, but such things happen.
Enter Elisabeth Bennet. She has next to nothing in money department (1000 pound which she will inherit after her mother´death), comes from a family the drawbacks of which have been discussed in the previous post, is not particularly pretty and has rather a sharp tongue, not exactly an asset for a young woman in her situation.
She gets a marriage proposal from one of the wealthiest men in the country, who on his mother´s side is a nephew of an earl. After she most rudely rejects him, they meet again by strange coincidence, he tries to make all the amends possible, bribes the man he hates to marry her youngest sister, proposes again and even goes so far as to tell her how unworthy he is of her affections. Small wonder that feminists love this story!