Drowning

Help- my mother in law is causing alot of problems in my relationship. Every time we are on vacation, she calls numerous times, wanting to know where we are , what we are doing, about to do, then at night calls to tell us it is time for us to go back to the hotel. She calls constantly throughout the day, and tries to tie up my wife for 30min-hour talking several times. Every weekend she calls wanting her to drive 2 hours to see and spend the weekend with her. Every holiday that we TRY to go and do something her mom calls and wont let her be with me, she starts arguments, threatnes to kill herself and tells my wife she doesnt love her till my wife gives in and does what ever she wants. My wife cant even spend a holiday alone with me without a huge argument,having to drive to see her, or her mom just pops in. When she comes over she wants my wife to paint her toenails, give her money to go gamble, she is now asking my wife to get her a new vehicle. My wife has stopped paying her bills, buying her furniture, paying her overdraft fees, etc since we got married 3 years ago, and now weekly she is calling wanting my wife to do something, pay this, find out about this, go do this, give her money for this, Recently we went on vacation and got a cabin, and her mom blew up, she told their therapists that she was mad she went off with me to a cabin and that she had never taken her to a cabin before. On VALENTINES day her mom threw a fit because we went on a trip, and even cried in their therapy session saying she wasnt going to see her that day. Oh and her mom even has a FIANCE- but she is constantly asking my wife to do things, be with her, pay, handle her business, things that I think she should be asking of her fiance. My wife has even in the past stopped in the middle of sex to answer her moms phone call saying if I dont ask she will drive up here. On her brothers wedding night her mother called him demanding that he leave and come over and replace her air filter!!!! He is now divorced, and his wife wont allow their mother to be alone with their child. SO SEE THE Problems SHE causes.Their therapist has even put her mom on a phone schedule with my wife, and tried to establish boundaries, but her mom said boundaries dont apply to her. She asked to come over a few weeks ago (after we had seen her the weekend before) and when my wife said no, she got upset, and then started saying that " oh your nephew might die in a car wreck and you wont see him again, and I am going to tell him you dont love him anymore". Help, I am at my end with this woman.