What do you meaaaaaan? Hahah... yes she said that she can't shapeshift Lona into Sea Witch but... you gain an ability that allows you to transform into Sea Witch. 
Just put it in your skills section and transform.
Oh... another person who lost a file in LonaRPG~ Yeah... it happens sometimes. Anyway... then just make a screenshot of error and tell me what version you have too because it will be clearer what the problem is and because I see that the most common LonaRPG problem for people is to go from old version to the new version of the game.