Women take on more student loan debt, and it takes them longer to pay off their loans.

The article blames the wage gap:

It’s been widely reported that woman today still earn only 77 cents for every dollar a man earns, and an earlier report from AAUW found that women who are one year out of college and working full time are paid, on average, just 82% of what their male counterparts are paid. This disparity in income can make it much harder for woman to achieve many of their financial goals — like buying a house, saving for retirement or paying off their college education, AAUW said. Moreover, the effects may be cyclical.

There are probably other factors too such as an increased likelihood of going to private college.