I agree with others that it's weird advice.
I do think that you should be careful about your Facebook privacy settings - make sure that what shows up to a non-friend search is enough to identify you, but no more (name, home-town, schools, profile pic). I also think it's wise if you are in a career where public image matters, to keep an eye on what and how you post. If you're in a career like this, you should probably be keeping an eye on what you *do* as well, as other people can post stuff about you without your permission (like pictures of strip poker games
) And personal and professional networking should probably be kept separate.
But I do think that Facebook is more intended as a family/friends network, not a social networking site. You have LinkedIn for that. Personally, I would tell the instructor that you use Facebook only for personal contacts and do not connect it to your business life at all, and ask whether she recommends having a second Facebook site for professional purposes, in addition to its normal use.
And I must say, I'm not sure what I would think about a lawyer having a professional twitter feed - celebrities/public figures sure, but your lawyer?