I had a friend like this. On top of clinging on to me for dear life she was also jealous and loved kicking me when I was down. Money, boys, travels. When something was lacking in my life she was the first to point it out and gloat. I was already living abroad. I changed my mobile. I blackmarked her email addresses. I cut her out of my life.
When someone is using and draining you like this, you have very little choice before you explode right into their selfish faces. I suggest you don't answer 90% of calls and become more elusive. Say that you're sorry about what's happening but you don't know what else to say and you gotta go because DP has just come home, the kids need tea, you have to pick something up, etc. Find excuses if you don't want to be straight with her. She'll (hopefully) get tired of chasing you and get the message.