Betty (Ella named her. I asked her for a name for my dress form, not expecting anything as she doesn't really know 'names' and usually she responds to questions with 'snack' or 'milk'. That day she said, "Betty". Ok, Betty, it is.) seems to pull it off okay. She may be the same size as me, but definitely not the same flab as me. Anyway, it's about 2 inches too short, so I wanted to crop it rather than send it away. The internet has a lot of great tutorials. I am still considering the idea of using the scraps to dress it up a bit.
Right sides facing, pin the cardigan to the desired length, lining up the seams and/or notions. Note that where you pin will be the length. Sew along the existing ribbed hem. Press open. Repeat with sleeves, if you so desire.
Tada! You have a cropped cardigan with original hem.
Pair with a cute dress.