Question 1091345
The answer is indeed huge:

<pre>
Number        Amount
of Days        Saved (cents)
——————        ——————
  1              1
  2              3
  3              7
  4             15
  5             31
  :               :
  :               :
  n             {{{2^n - 1 }}} 

—
So after 75 days, she will have saved {{{ 2^75 - 1 }}} pennies, which is  {{{ 3.777893 }}} {{{ x 10^20 }}} dollars…  way, way,  more money than is circulating in all the world's economies.
—
To put that amount in perspective, it would be enough to pay off the entire national debt of the USA ($19,000,000,000,000), not just a few times, but over 19,883,000 times!