Not such a pioneer?

... the case for improving women’s rights had been put increasingly in prior years: by Mrs Makin in 1673, by Mary Astell in 1694, by Daniel Defoe in 1697. Steele, Addison, and Swift urged that women should be given a better education. A woman under the pseudonym of Sophia published Woman Not Inferior to Man in 1739. Catherine Macauly, in her book Letters on Education, maintained that women and men should get the same education. (This was reviewed approvingly by Wollstonecraft.) A Declaration of the Rights of Woman was published in France in 1791. Thus, Wollstonecraft’s work was one of several that ultimately led to the enfranchisement of women in the Twentieth Century. The vigor with which she put her case probably sharpened the debate and drew greater attention to the situation of women.

http://www.humanistictexts.org/wollstone.htm

And this was just in English. Mary also had access to French texts at home, and she read German too. Nothing comes out of nothing: she drew on many streams, just as she in turn gave to many others.