You hit right on target when you alluded to the role of mothers in determining a girl's interest or lack of it in Mathematics.

Mothers can't give what they don't have to their daughters. Most mothers are Math-challenged!
You want girls to get interested? Get the mothers interested!

Perhaps a free program to teach mothers basic Mathematics could help.

Mothers could progress from basic math to middle level and beyond, so that they can acquire enough math skills to help their daughters with homework.

With a better understanding of Mathematics, mothers could turn activities like shopping, banking(going to the bank)and even cooking into math-teachable moments.