IIRC she outright spoils two puzzles, and in both circumstances only after an error from the player (wrong solution in a puzzle before dungeon 3, leaving a room before solving a puzzle in dungeon 5). By comparison, the tombstones you find lying around spoil much more stuff by just telling you what to do instead of giving hints through riddles.
Now, I agree she's annoying, I agree telling the player how to solve the puzzles after small errors is too much, and I agree her tendency to re-state the obvious is beyond comical, but the hyperbole around Fi is probably even more ridiculous.