Facebook: privacy setting on activity?

[The Kids]

I have the biggest problem right now.

So, i have included my mother on a list called "family" on facebook, and i have made it so that the family list couldn't see my wall, my updates, my tagged photos, and my activity, etc.

But just a while ago my mom told me that she thought my comment on one of my friend's picture is funny, but quite rude. I asked her what comment, and she showed me on her computer.

On her facebook feed it says...

(my name) commented on (my friend's name)'s photo
(insert comment here)

HOW IS THIS POSSIBLE? I HAVE MADE IT SO THAT THEY COULDN'T SEE A THING. i don't think it's because my friend's profile is visible to everyone. I have used my girlfriend's account (who is not friends with my friend on facebook) to view my friend's profile. I found out that my friend's profile is private and you couldn't see her wall as well. I have also logged out and viewed my friend's profile anonymously and I couldn't see a thing except her profile picture. So I don't think it's because of my friend's privacy settings. But how the heck was this possible? How come my mom could see my activity? What am I supposed to do? I can't have her see all the comments I post on other people's walls or notes or photos/videos.

I'm pretty sure my mom couldn't see my status updates though, because she has mentioned that she couldn't find my wall on my profile. But how come she can see my updates? please help me. Which setting should I edit?
btw, my mom is not friends with my friend on facebook either. Like J-weg said, it doesn't matter what kind of security i have on my profile. If my friends are the ones receiving the comment, their privacy settings are the ones that are gonna be effective. But my mom is not friends with that friend of mine on facebook, so I don't understand why she was able to see the comment

[J-weg]

Doesn't matter what security you have on "your" wall.

Because in this case it was "your friends" wall that was getting the comment.

Your mom will be able to read anything you post on a friends wall as long as the friend doesn't have privacy settings that block your mom out.

sorry kiddo

[Lenny Gilmore]

You have your mother on a family list and I'm sure that's enough to see what you are writing on your friends' walls. You should review you privacy settings again.

Facebook Security and Privacy Best Practices
http://deletemalware.blogspot.com/2011/0...-best.html