Thoughts on the Education of Daughters: With Reflections on Female Conduct in the More Important Duties of Life was first published in 1787 by her friend Joseph Johnson. It was written after she spent some time as a lady's companion to Sarah Dawson, who she did not care for. The book covers many things from how to raise a child to advocating for better education for women. Mary gets some backlash for this today, as much of what she speaks on is about how the better education is about how to make a woman a better wife and mother. However, she does encourage women to teach their daughters some kind of trade so that they may support themselves if need be.
Rorueso. "Thoughts on the Education of Daughters", 1787. rorueso.blogs.uv.es/2009/10/22/thoughts-on-the-education-of-daughters-1787/.