I need help with facebook customizing privacy settings please?

[flipflopchick]

I went into my privacy settings on facebook & blocked my mother-in-law from viewing my wall posts without un-friending her because if I un-friended her she would notice & probably get angry, but honestly I'm sick of her reading whatever I post & making little comments about it. I did this but I think she can still view my stuff, what am I doing wrong? Anyone who is really good at facebook privacy setting plz help. And yes if I cant figure it out within a day or so I'll probably just delete & block her, but I was trying to be nice about it.
Please dont say that its not possible because it is, I think its working but she can view everything up until the time that I blocked her so she can still read old posts which i dont like, and when I like another friends status that is showing up also.