Fawcett had, according to Umbridge, dispensed a potion to another student and attempted to entrap the other student in misbehaviour. U suspects other students of involvement.

But then U seems to suspect nearly everyone of nearly everything. And punishes them for as much of that as she can find barest pretext to justify. She's always been a mixture of hubris and paranoia, but that's grown more potent recently. Notably so since my last summons to the school.

Nothing of use to Razzer in her office, by the way. We did look.