How to let her know I don't want to be friends?

I have this "friend" and I don't know how to gently break it to her that our friendship won't work out. She's FULL of drama, and is constantly going back and forth between guys, and I hate drama. All she ever wants to talk about is her boys issues and how "messed up she is" (in her words not mine). Also, she's always saying she has migraines EVERY SINGLE DAY. I totally get it, because I get headaches all the time also but it's really annoying to hang out with someone who is always complaining that they don't feel well. And she calls me, every single day and multiple times. For example, yesterday she called and talked for two hours about one guy and when I told her my mom had to use the phone for a patient,and to please at least wait an hour until my mom's done, she said "OK I'll call right back" WTF!? and then she calls back after ten minutes. And when I don't answer the phone she just keeps calling. Once she called me nonstop for twenty minutes. I just can't deal with any of it anymore. She never wants to see a movie, or go shopping. It's always the same thing : sit in her house and complain about her life. How can I tell her I really can't take it anymore? it a NICE way.