I'm glad it works for her, but in my experience, the more layers and folds there are, the higher the possibility for shifting and wonky strips. It's slower, but I cut mine with a 24" ruler on a 36" mat, with the fabric only folded once (the way it comes on the bolt). I don't have any trouble holding the 24" ruler in place. After 3-4 strips, I stop and make sure the cut is still square with the fold, using the lines on the ruler. It's no big deal to re-square it, if necessary.
I agree that her mat desperately needs replacing!
