How can I keep my mom from seeing my friends' facebook posts without unfriending her?

[Leo D]

You have to be a bit more clear on what exactly she's seeing.

The posts about you are called "tagging". When some one tags you, then other people know that their posts are talking specifically about you. Block her from your tagged posts. It's in the same place where you blocked her from your time line.

Aside: The easiest thing to do is to have two accounts: a real one for your family life, school and job; and a fake one for your closer friends and interests. This way, if facebook ever rolls out a new privacy policy that renders your blocking public, you won't have to worry about private stuff leaking into your public stuff.

Facebook didn't really include a way to block people from seeing what you do with other people's content (joining an Interests page, playing a game, commenting on a friend's status update, liking a subscription's picture), other than asking them to opt out of receiving those notifications. The link for that opting out is obscure. I don't remember it honestly. The only way to do this for sure is to not interact with content that you don't want some one finding out about.