Just now was doing a node in the PvE event. I was fighting Iron Fist. He was stunned I used hair meddle at 4 purple and it would not change his attack tile to my side.
Is it possible you ran into this bug: https://forums.505go.com/discussion/61618/medusa-bug-different-circumstance-devs-aware
The gist of it is that if a tile is moved by her power (and should be stolen), but then moves to another spot again because of matches caused by the swaps, the power loses track of the moved tile and fails to steal it — the spot to be stolen now contains a different tile.