facebook - friend question? ?

[I love me!]

this friend I don't want to include on my facebook as I really do not want to be friends anymore really. I outgrew our friendship as I matured. She has asked for the 2nd time to be friends. I email her just to be polite but I do not want to allow her in as a friend. What can I do? I use my facebook to really share my life with my real friends and don't want to include her. I thought she'd get the hint when I ignored her the first time. Can I admit her but not allow her to read anything? Or is that too rude if its even possible.
its sort of touchy. she was my bride's maid. I am mad at her for never responding to my email 6 years ago when my special needs son was born. it was cruel of her. and now that she;s a mom and all enlighten she wants to be friends.
could i just email her and say i use facebook for a local group of friends and would rather just email ?