I can remember two cases, though their may have been one or two more.
Apparently not used to using her magic as a weapon she:
-accidently mind rapes one into killing its own comrades, or awakened it's host to it's own existential horror.
- transmutes another into a ponnequin, which, since it was in mid flight, promptly falls to the ground and breaks up.
Since this is in the middle of a chase we don't linger long enough to see if the ponnequin transmutes back into a broken crystal Pegasus or any hint to whether it was still aware as a ponnequin.
Twilight does witness the second one though and I remember her initial reaction essentially amounting to being proud that her friend was powerful enough to do that, but that it also raised some disturbing questions she would have time to ponder once she and her friends were not fleeing for their lives.