On hearing this, my first reaction was "Huh?"
Not counting fictional females and goddess figures, like Liberty, four women have appeared on U.S. money:
- Most recently, Sacagawea on the dollar coin
- Susan B. Anthony, also on a dollar coin (replaced by Sacagawea's image)
- Martha Washington, on 1886 and 1891 $1 Silver Certificates, on her own, and on the 1896 $1 Silver Certificate, with husband George
- Pocahontas, whose image is depicted on 1869-1878 $10 notes
Of course, that's nowhere near equity in depictions, but it's certainly not "never."