Ok. THIS is why I don't have a Facebook account any more. That South Park episode was right. To be honest I wouldn't want my mother reading what I post on The Escapist when I've had a bit to drink (never drink and internet kids) or when one of those weird, and sort of gross, threads turn up.
I'd suggest giving it a day, and then sitting down with her and talking about what's going on. What are you being punished for? Why does she feel so bad that she feels you deserve to be disciplined for your actions? Also why didn't you add her on Facebook, and what harm would it do to just do that?