Gosh I could have written your post! I have given up worrying too much about MIL's (and FIL's) presents anymore. I usually leave it up to DH to come up with the ideas and he usually comes up with something really exciting like petrol vouchers or golf balls! I used to hate that but just don't worry anymore.
A book, magazine subscription? Does she have any hobbies or play sports? Something to do with those? Another $10 platter

. A "Grandma/Nana" coffee mug full of chocolates?