You graduate from college(4 yrs $40- $50K), go to Law School (3 yrs $100-$150K) study for the state bar exam(3-4 mos), take and pass the exam, get your license then apply to all the law firms that handle discrimination law and hope that you get selected for a position paying $60-$70K p/yr. There are too many lawyers out there already!
You haven't provided anything close to the information I would need to give you an answer.
When was the parenting plan signed by a judge? Was the mediation part of a petition to modify the original parenting plan? Were you represented by an attorney during mediation? Was this court ordered mediation? Who was supposed to present the mediation agreement to a judge for signature.
What part of what parenting plan is she failing to comply with? Why is she failing to comply with it?
It is very, very unlikely that calling the police would be the right move. If you believe she is in contempt of a signed (by a judge or court commissioner) parenting plan and you can demonstrate that she doesn't have a reason to ignore the order, then you file a motion and you ask a judge to find her in contempt. That is your appropriate remedy.
As far as mediation? This was mediation, not arbitration. If you were represented and she was not, it seems very reasonable she would have a "remorse" period to take back her agreement. Otherwise, it is entirely possible that your jurisdiction allows parties to have a 72 hour remorse period to change their minds.