Sometimes there are straightforward non-technical solutions to complex technical issues.
Be the mean parent.
Take the iPhone away immediately.
Remove her immediately from any family or 'unlimited' post-paid phone plan.
Give her absolutely zero opportunity to earn the iPhone back for at least a year.
Her actions, attempting and/or succeeding in overriding parental controls by any means, is abusing a privilege.
Abusing the privilege means losing that privilege.
So she's absolutely lost the privilege of having a smartphone for the next year.
If she truly needs a phone, to call home for a ride, or for added security when using public transportation, a $30 Android flip phone will have virtually no smartphone features, a very minimal browser, and no App store. A basic flip-phone will be useful for T-9 texting using the number pad, and voice calls, exactly what you need for basic communications and true emergencies.
Set her up with a low-cost month-to-month pre-paid account. (If the days and minutes run out, the phone stops working EXCEPT FOR emergency calls). Make her responsible for the monthly prepayment. A $10 prepaid card with a wireless carrier typically provides 30 days of use and a low number of airtime minutes, perhaps 60 or 90. That also has the side-effect of calling one's friends and talking for 'hours' less appealing. Larger dollar amounts can purchase more days and more minutes of service, but the idea is to teach some restraint and self-control.
If you're lucky, she'll eventually come to understand that earning back a substantial privilege like a smartphone requires learning to be a responsible human all the time.
If she is a child of divorce, and this is a case of ex-spouses and/or grandparents competing for the child's approval with extravagant gifts, then this presents an opportunity for all of the adults involved to begin a discussion about setting priorities and working together to raise a responsible child who will ideally become a responsible adult.
To echo the other individual who already replied, the dangers of abusing the 911-emergency response system are obvious. The lives of others could be at stake if a 911-call cannot be promptly connected when seconds count because a clever teen is repeatedly dialing 911 and hanging up to thwart the phone's parental controls.