If you want to fashion the crochet into a sewed item I would prepare the crochet before I cut. Determine the size of say the pillow you'd like to make. Then using some light weight sew in interfacing sew the interfacing to both sides of the crochet at your predetermined measurement. You should then be able to cut the crochet beyond the interfacing and treat the crochet as fabric.
If you are not comfortable trying this on your Mother's items first, use something you've made or an item from a thrift store. Let us know how it turns out.