Even though she is pictured with a Dominican habit, St. Rose of Lima was not a religious nun.
Whenever St. Rose of Lima is depicted in painting or statues, it appears that she is wearing a Dominican habit and is a religious nun.
However, while she greatly desired to enter a Dominican monastery, her father forbade it.
Instead, St. Rose of Lima lived at home and became a member of the Third Order of St. Dominic. This means that she was technically a lay member of the Dominican Order and lived in the world, outside of a monastery.
She did wear a habit that is specific to members of the Third Order, and also made a personal vow of perpetual virginity.
St. Rose of Lima led a life similar to St. Catherine of Siena, who was also a member of the Third Order of St. Dominic.
Both women were not religious nuns who lived in a monastery, but instead lived out their lives in the seclusion of their own homes.
Currently, while Third Orders still exist today, the religious habit is no longer worn by members except in death.