You can see when she finished cutting the straight strips that the fabric is double.
I watched both videos (were there three?). Jenny Doan has a good method, but when you start the binding at the very beginning, you can measure where the ending will be cut! ! ! Lay the folded-in-half binding on the quilt where you will be sewing it - front or back. The beginning can be eight or nine inches from a corner. (I do eight inch potholders with this method.) Open the binding flat for a few inches and fold the top edge of binding strip down so that it lays along the edge of the quilt, making a triangle. Press this triangle very well; steam or starch is good. Refold the strip and start sewing right near the corner, about seven or eight inches from the beginning, and turn your corner as usual. Go all around the quilt until you get about 10 to 12 inches from where you started sewing. All you need for overlap is the 2.5 inches of your binding. If you have more, cut the end binding strip at the base of the triangle: that is the perfect length. Now, open both ends flat, bring them right sides together and twist them so that they are at right angles; just the same way you sewed all the other seams on the binding. Be sure you are sewing from side to side. If it is wrong, just twist them the other way. Sew on the crease of the triangle you pressed in at the beginning.
I also finger press that seam open to reduce bulk at that point. Be sure to test before you cut off the little triangles.
Happy binding.