Well, I think she may have just pleated the fabric at the bottom, but I can tell you how I did the one I made... It turned out well.
First of all, you need excess material. I don't know how big your shirts are, but I had an enormous shirt (you could also just use other material you have around). I cut a couple bands off the bottom of the shirt and set them aside. Then I used a well-fitting shirt to trace the sides (with seam allowances!) on the larger shirt, and sewed that into a tube so it fit me.
Then I cut those bands and sewed them together into one very long strip, about twice as long as the circumference of the bottom of my shirt. Now, you could probably sew them on, pleating as you go, but I gathered mine... and then you just sew it onto the bottom of the tube you've made, and voila.
I know there are different ways of gathering. Some people just sew a little at a time with a large stitch, and gather as they go. I zig-zag-stitched over a thread, anchored one end of the thread, and gathered it that way. Personal preference, I guess.
Am I understandable?
hey! thats a really good idea! and here i've been bunching and scrunching while i tried to sew and keep it all even.. duh!
thanks for the tip!