Rita immediately takes a casting stance--she doesn't immediately fire off a spell, but she wants to be ready in case a) the 'prankster' tries anything, or b) she loses her temper.

Standing right where she is, she scrutinizes first Cassandra, and then the note. That's definitely the magnet she used, for one thing, but--surely the culprit wasn't smart enough to notice it that quickly! "A likely story," she scoffs, but there's just enough flicker of doubt that she still doesn't move; this lady is kind of old to be pulling stupid pranks...probably. "You could've easily made that note yourself!"