Positive reinforcement works much better than negative. Focus on when she does well and have a reward chart. For every day you don't get a call, give her a small reward, an extra story at night, or something small that she likes.
3 days, something more special and if she has a good week, she gets the big reward.
Kids like things that they earn, more. My oldest used to get between 5 - 10 M&Ms from her piano teacher at that age, after a good lesson and they meant more to her than if I had bought her a whole bag.