I had the same situation awhile back, and made a big to-do about it. Tried all kinds of folding and twisting things. But I finally just stitched to the corner plus 1/4" beyond into the quilt, tugged the next edge till it was almost a straight line and pivoted the presser foot and stitched along the next edge and continued as before. So easy. Hope this makes sense!
The Beautiful Cumberland Plateau, Tennessee USA