How to tell my mom I don't care about her FB nonsense?

[Telling It Like It Is]

My mom has been on Facebook non-stop and even wrote a status about my boss (who she's friends with). My boss' sister uses her account for games and invites my mother to play. While my mom ignores the game invites, she is virtually "pissed off" that my boss' sister uses the account to play games.
My mom called me last night to tell me all this drama and I really don't have time for it - I had a meeting last night and today I was on deadline and have a lot of responsibililty at my job. I don't want to hear this nonsense with her and FB, but she's on all the time AND writing statuses about my boss!!!
My mom has no friends in real life and even though she has my 10 year old sister to take care of, she has plenty of down time, during which she comes off immature to people.

When she calls me, how can I tell her i really don't care about fb and that I don't want to hear about it (in a nice way,of course!)