She is only folding lengh-wise and that it's not too difficult with a long enough paper. Also the myth was busted properly in mythbusters season 5, "seven folds":
"They decided to make their open big 170' x 220' piece using 17 rolls of paper joined together with double-sided tape. An experiment this large required that they go to Moffett Field and setup in one of the blimp hangers there.
Using the traditional technique of alternating folds length and width-wise, they were able to get eleven folds."
What I mean is that it's much easier to physically fold a stripe of toilet paper (one person and a lot of walking) than a huge sheet of paper which needed a team of 20 people to be fold.
And again, it's much more difficult to fold a paper alternating folds length and width-wise than only lenght-wise.
I'd say the math and her grasp of how to use it to solve a problem like this was far more impressive (especially for a then sophomore in HS) than any actual folding that may have occurred.
I worked it out this afternoon, and its not too terribly difficult to get a nice closed form solution (as opposed to a recursive (or iterative one). Its mostly a bit of geometry with some cleverness moving things around to get a nice closed form solution. The only advanced math is a geometric series that comes up at the end, which gives the final fully closed form solution for the length of the paper given a thickness, initial length, and the number of folds. It becomes easy then to solve for an initial length for a number of desired folds.
The fact that she was in high school when she did this though, is impressive. Any teacher with a bit of calculus would have been able to guide her though, once he saw where she was headed.
"They decided to make their open big 170' x 220' piece using 17 rolls of paper joined together with double-sided tape. An experiment this large required that they go to Moffett Field and setup in one of the blimp hangers there.
Using the traditional technique of alternating folds length and width-wise, they were able to get eleven folds."
http://kwc.org/mythbusters/2007/01/episode_72_underwater_car...