Wow! I just watched her Drag Race quilt tutorial and she is a great teacher. I don't know which one shows how not to bow your strips, but I think I'll fun finding out by watching her tuts.

Here is a video of Donna making a rail fence quilt with striped units. If you advance to 7:00 (minute) point she is sewing and talking about bowed seams.

https://www.youtube.com/watch?v=SSxm0YVgmfM&t=48s