Hi, I agree with the others. Does she have any indication...as in has there been ANY discussion anywhere that there might be a disability of some kind, whether emotional, behavioral, learning challenges, adhd, sensory (which I woudl suspect if she got so upset about the line issue.....) If a child is even suspected of a disability and you write a formal letter (certified, return receipt tot he principal and Special Education department) if you do not have an IEP already (an IEP is an individual education program to support kids with unique learning needs due to a disability)....
Anyway, writing that letter to ask for an evaluation of her behaviors can afford you protection under the law. ten days for kids on an IEP is the max. before some specific guidelines have to take place.
If you let us know if she has had any other issues, behaviors, learning issues in school it will help us guide you.