There were witnesses who watched her drive in to the school parking lot and attempt to park for 15 minutes. She was in a conference and if the witness says she wasn't consuming the alcohol/drugs there then she had to have done it before she drove to the school. Yeah, these facts could support an OWI conviction.
The officer did not observe her driving.
He had no sworn statement or warrant.
Even if you take the report from the witness, what road or highway was she operating on ?
Also, I live in Maine. Every native Mainer expects you to know where every town is and every business that has operated in the last fifty years. (Also, check my tagline)