Upvote:2
The sacrament in itself is sufficient for giving grace, but the dispositions of the recipient can hinder the action of the sacramental grace.
Discussing whether one can receive the Eucharist daily, St. Thomas Aquinas writes (Summa Theologica III q. 80 a. 10 co.):
There are two things to be considered regarding the use of this sacrament.
The first is on the part of the sacrament itself, the virtue of which gives health to men; and consequently it is profitable to receive it daily so as to receive its fruits daily. Hence Ambrose says (De Sacram. iv): "If, whenever Christ's blood is shed, it is shed for the forgiveness of sins, I who sin often, should receive it often: I need a frequent remedy."
The second thing to be considered is on the part of the recipient, who is required to approach this sacrament with great reverence and devotion. Consequently, if anyone finds that he has these dispositions every day, he will do well to receive it daily. Hence, Augustine after saying, "Receive daily, that it may profit thee daily," adds: "So live, as to deserve to receive it daily." But because many persons are lacking in this devotion, on account of the many drawbacks both spiritual and corporal from which they suffer, it is not expedient for all to approach this sacrament every day; but they should do so as often as they find themselves properly disposed. Hence it is said in De Eccles. Dogmat. liii: "I neither praise nor blame daily reception of the Eucharist."
The "woman [who] regards the Eucharist as merely a symbolic act" of your second scenario disbelieves in transubstantiation and is thus a heretic; she thus receives "unworthily, [and] shall be guilty of the body and of the blood of the Lord" (1 Cor. 11:27).