When Caller ID Bites You in the Tush

Sometimes, ok more often than not, when Tim and I go out and I have had a few drinks I tend to pick up the most random person in the room. At Tony and Carin's wedding it was Donna Lavalli, a stay at home mom of 2 little girls who was way more interested in the Wiggles Christmas Special than she should have been. Last year at he carnival it was Jodi in the beer garden of the American Legion. She was with her boyfriend and told me all about how she was a crystal meth addict when she found out she was pregnant, but was able to kick the habit by the time she gave birth. There have been others, but I choose to forget.
One who I have not forgotten was the lovely Cassandra. We met her at the Mafia Hang out one night when we were out for Tim's birthday a few years ago. Tim really liked her husband because the had car dealerships in common and were both Nancies when it came to their fathers. They had a kid a little younger than Abby, and we tried to be friends with them. As we have all learned from watching Sex in the City, and from our own experience, you can't have a relationship with someone you meet in a bar.
I tried really hard to be friends with this woman, but eventually I had to give up. She is pretty much an alcoholic who would section her days into smoke breaks and cocktail hours, which just isn't my style. So one day when I was first pregnant with Nora I just stopped taking her calls. I have caller id for a reason and she was it for a while. So I successfully avoided her (and kind of felt guilty about it) until she sent me a letter all about how she thought we were such good friends and that her little Lucy needed a best friend and she wanted Abby to be it and blah blah blah. I was slightly horrified by this, and almost called her, but I stood strong. I didn't want to be friends with this woman, and I wasn't going to try to be so that people didn't think I was a total bitch, so I just ignored the letter.
So this was all about 2 years ago and I have not looked back. Until last night...
So Tim and I are watching the Real World Reunion, its about 11:15 pm and the phone rings. Odd, no one calls our house that late unless it is one of his parents calling to tell us about a fight they are having. So we don't recognize the number on caller id, but I tell Tim to answer it anyway in case someone we know is in trouble (if you are calling that late then it must be important, right?). So Tim answers and starts freaking out, but won't write down who it is then hands me the phone (the jerk never covers for me!), and lo and behold it is Cassandra, calling (let's be honest, she was drunk dialing) me after 2 years at 11:15 at night.
She wants to hang out.
She had another baby girl.
They moved.
What do I do? I really can't convey to you how much I do not want to be friends with this woman, but I feel like my Karma will be totally fucked if I blow her of again. Am I obligated to call her back because I said I would? And if I do do I have to hang out with her?
Help!