How can I prevent Facebook friends commenting on my other Facebook friend's walls?

[Goo]

I have a Facebook friend who has the annoying habit of posting comments on the walls of my other Facebook friends (even though she is not their Facebook friend). Somehow her being my Facebook friend enables her to leave comments on any wall where I leave a comment- The result is friends who have no idea who this person is think she's a nut- I like her, but some of her comments are strange and can be taken as offensive. For example, I commented on a Facebook friend's photo, and this other Facebook friend commented 'someone needs to have their teeth bleached'. The reaction was 'wtf are you'? HOW can I fix it so nosy Facebook friends can't leave posts on the walls of my other friends?
How do you react when people you don't even know can somehow leave comments on your Facebook wall?
I don't mind my friends posting on my wall- what I don't like is when my friends post on my OTHER friends walls (people that they are not friended with). Somehow anyone on my Facebook friends list can post on the wall of any friend, provided I made a post on that same wall (for example, a comment I left about a friend's picture, then another Facebook friend left a comment there, despite not being a friend of the first person)

[Yikes]

Block them from your wall.

[J.C]

block the person and delete him/her

[JL]

Yes you can. The only way is to set your wall not viewable to that friend.
Since the facebook page is updated now, I"m not sure how to do that now, but there is a feature that can do that.

Hope that helps.
=D