The example I gave you is the same idea but I don't know how it was constructed. It was the only example similar I could find. You're right - on that one they may have used a hemstitch for the edges then used the holes created to crochet the edging and strips to the cloth.
Aha - here is another one that has some close ups - the last picture shows one of the stitching where the crochet is attached:
http://www.etsy.com/listing/84926481/crocheted-bedspread-with-linen-inserts
The crochet in that one is very similar in style to my grandmother's but the overall piece is more elaborate. Like I said, she only had two strips of crochet and the edging was narrower. The style and weight of the crochet looks similar, though hers is now ecru color. I don't know if that was the original color or if it has just turned it with age.
I'll be back down at my mother's for Thanksgiving and will try to take pictures.
ETA - just found a shot my husband took earlier this year! I'll edit it and upload. Back in a few minutes.