It is our duty to take good care of our parents, the good book encourages us to do so. "Honour your father and mother that your days may be Long on earth ". Your friend's parents should understand the situation of things. Let your friend explain to them how much she earns, so they won't be expecting much from her, when she doesn't have much to offer.
So far, she is doing well. Tell her not to derail in taking care of her parents.