I have personally known 2 women now who chose to become nuns, but midway through their education, had a change of heart. Did God call them to these positions but decide they’d be better fit as mothers?
Who knows? Only God knows the human heart. Vocations are mysterious and often take people on paths unexpected and rarely straight.
People enter religious life for many reasons. It’s an old observation among those of us privileged to be members of religious orders that, “You enter for various reasons; but you stay for other reasons.”
The most radical reality of our faith is that God deals with us as free persons (Gal 5:1). Life isn’t some game show where there is Door #1, #2 and #3 and you have to guess which one hides the big prize and which one hides a billygoat.
We are free to converse with God, ask what God wants, and then, as in any loving relationship, choose what we want. We know what God wants when we know the deepest and truest desires of our heart and soul. Those desires are planted there by God. But we are free to choose how to respond to those desires. God plants the desire to serve others in our heart. We are free to do that as married, single, or persons in religious life. Sometimes we may feel called to one state for a time and then find ourselves yearning for another path. One doesn’t change permanent lifetime vows and commitments lightly. But many people who leave religious life for another way of loving and serving do so after much prayer and spiritual direction. God is with us through it all, and God’s grace and love can come to the world through us in many ways and states of life.