D.W.
My parents were very strict, too. I was constantly grounded despite being a good kid.
All the experts say that kids want their parents to set limitations and hold them accountable for breaking the rules. She's 14, you're the parent. Be firm in making and enforcing the rules. If she is getting high, who knows that it's from. Some things kids are doing today are really, really dangerous.
It may take an uncomfortable conversation, but you'll need to ask her and find out. I agree that her cell phone is a privilege, and should be taken away and monitored if it's abused.
Yes, we all do stupid things as kids, and I regret the rather benign things I did.....being too sheltered can have negative consequences, too, but in the end, it's our job as parents to make sure our kids are safe and on the right side of the law.