So, for Bellarmine, the will remains mistress of its act because the motion is in a way in its power
On Bellarmine's view, then, the answer to the objection is this. Although the will needs God's prior motion and application in order to act, it is always mistress of its act, because it has that motion in its power to some degree, in the way just explained.
Once God's motion is given, the will cannot fail to be moved; yet it is always free in acting, because it was in its power not to be moved by God, namely by not disposing itself, through that negative determination, to receive his motion. That was up to the will.
Latin
XV. Itaque ad argumentum, ex Bellarmini mente, dicendum est, quanquam Voluntas ad agendum egeat Dei motione praevia, & applicatione ad opus, illam tamen semper esse actus sui dominam; quia nimirum motionem illam quadantenus habet in sua potestate, qua ratione jam expositum est. Et quamvis posita Dei motione impossibile sit quin voluntas moveatur, voluntatem tamen semper in agendo liberam esse, quia fuit in ejus potestate a Deo non moveri; nempe se non disponendo per negativam illam determinationem ad motionem Dei recipiendam, quod erat penes voluntatem.