advice

I have a friend and an acquaintance that seem to be your typical "fair weathered friend." They are only around when they choose to be. I don't even hear from the acquaintance but on occasion, I'd say every few months or when she wants to cry and she can't call anyone else. Neither of them have come to my kids parties, the birth of my son or my baby shower. Its always one excuse or another. The acquaintance seems to be all about the drama and calls to whine about something or other or when she needs a sitter for her 9 year old son. I have gotten to the point where I just don't answer her calls. Now I've moved close to her a few streets away and I am afraid she's just going to drop by. After months of not answering her calls and Instant messages etc. You would think she would get the hint but she hasn't. My therapist tells me to just tell her I don't have time for her drama but as bluntly honest as I am I can't bring myself to that point. What do you do when your friend or acquaintance has too much drama or is a fair weathered friend type?