Rin: SHITAKE MUSHROOM! And I thought Fairy Tail was nonsense!
All the rest: WHAT DID YOU SAY!?
Rin: n-nothing! Hehehe...*creates a magical barrier between them and the fight*

Now, it really is a movie, because Rin is behind a barrier that technically sent her to a different dimension. It's like she's still there, but not. So technically, she's there, but away from the fight. It's not a "portal", so HA, LOOPHOLES!