Female's take:
Also, question for those more educated. If she was handcuffed and sitting in the patrol car, at what point should she have been read her Miranda Rights? They had her sitting in the car for 20 minutes. That's questionable to me, but again, I'm not sure of exact procedure in that situation.
Advisement of Miranda rights isn't mandatory simply because one is being arrested or detained. If the Officer wanted to ask her questions about the alleged crime, then he would need to advise her of those rights.