How to "break up" with a friend

I've got to get rid of Rachel.

She sucks my time and energy. She's off her meds, so all she talks about is her new husband's ex-wife and the battle for child support, court dates, rude phone calls, how they are so broke, how she just *loves* those girls.

I tried to tell her she shouldn't have married him. He's a nice guy, but she's only 24 and he has two kids and a alleged crazy ex wife. She is a Daddy's girl/attention whore/drama queen as it is....no way is she going to take a backseat to his kids and ex-wife for long term...why am I even spending time on this... I dont' really care.

What do you say to someone like that? I stuck it out with her through July because she asks me to be in her wedding, and I thought it would be nice to do so, since she asked me in January. OHMYGOD her wedding was so over the top! and her parents must have spent 20k on it. Such a waste of money. She had a cancelled wedding a two years ago. She makes bad choices, and she is so insensitive to others. I am tired of it. I don't have the energy. She almost never asks about me, and if she does, she is just waiting until I say my piece so she can go back to her life. Irritating.

So, I'm going to start avoiding her phone calls first. And when she gets me unprepared at work, I'll just do the "Yup", Uh hun", "Oh, really?" crap until she hangs up...Although I've been doing the "Oh, someone needs me, I've got to go!" and the "I'm late for a meeting!".

I'm not sure what to do. I could just sit down with her and tell her the truth, but she'd just bawl and carry on for days, and I'd rather have a gentle goodbye.

Did I mention her step children are brats?