According to Roman Catholicism, Mary loved God of her own free will. Does her love mean less to God because grace protected her from sin?

Question

The Immaculate Conception shows that God could, in theory, protect each person from the contracting the taint of original sin. An argument as to why God allows His children to contract original sin is because He wants their freely given love. Doesn't the life of Mary suggest that we can freely give God our love and not have the taint of original sin? Doesn't Mary's freely given love suggest that even when our wills are protected from sin by God's grace, our love is meaningful? Why doesn't God create us all like Mary? Without original sin, protected from sin by His grace, and still able to love Him of our own free will? Or does love only matter to God if it comes from sinful people who might choose otherwise? If so, how could a just and loving God punish them, if he could have protected them from sin by His grace but chose not to?

Answer 1

Merit

I think by "mean" you mean "merit", "Divine reward for the practice of virtue."

Merit is not obtained by our own abilities (thus, "working harder" doesn't always increase our merit) but by our cooperation with grace:

The reward given for good works [merit] is not won by reason of actions which precede grace, but grace, which is unmerited, precedes actions in order that they may be performed meritoriously.
_{—2^nd Council of Orange, Denzinger 388}

Merit is divided into:

• Condign (de condigno)

  Due to a person for some good he has done. Generally applied to merit before God, who binds himself, as it were, to reward those who do his will. The conditions for condign merit are the state of grace and a morally good action. The beneficiary is the person who performs the good act and not someone else. Condign merit is based on the revealed fact that God has promised such a reward. Thus we condignly merit an increase of the virtue of faith by every act of faith we perform in the state of grace. (Etym. Latin con-, thoroughly + dignus, worthy: condignus, very worthy.)

• Congruous (de congruo)

  Equitable and proper that God should grant what is asked or expected of him. Commonly applied to merit, it is distinguished from merit strictly so called, the latter being known as condign. Congruous merit is not precisely merit, but well-founded expectation. It refers to "gaining merit" for others, obtaining from God what a person in the state of grave sin prays for, receiving the gift of final perseverance and, in general, all the blessings we are confident God will grant, without having the absolute assurance that he will do so. Congruous merit is associated with the divine goodness, where condign merit rather depends on God's fidelity to his promises.

Blessed Virgin's merit

Réginald Garrigou-Lagrange, O.P., Mother of the Saviour and Our Interior Life, ch. 2, article 4 "The Perfection of Mary’s First Grace", § "Was Mary’s First Grace higher than the Final Grace of all the Angels and Saints taken together?":

Mary could obtain by her merits and prayers—even on earth, and from the time when she could first merit and pray—more than all the saints together, for they obtain nothing except through her universal mediation. Mary is, as it were, the aqueduct which brings us grace; in the mystical body she is, as it were, the neck which joins the members with the Head. In short, from the time she could merit and pray, Mary could obtain more without the saints than they could without her. But merit corresponds in degree to charity and sanctifying grace. Hence Mary received from the beginning of her life a degree of grace superior to that which the saints and angels united had attained to before their entry into Heaven.

She merited more than all the other saints combined: "Mary had merited more by the easiest acts [e.g., sweeping the floor of their house in Nazareth] than the martyrs in their torments because of her greater love." Since she had greater charity, being "full of grace (κεχαριτωμένη)" (Lk. 1:28), she had greater merit.