Natalie's bad habit

So lately whenever Kate is doing something to Natalie that she doesn't like and gets fed up she pokes her in the eye and sends Kate off crying. I came home last night and Kate was up out of bed crying so I went to check on her. She wouldn't open her eyes and kept telling me that her eye hurts. I looked at her eye and it was all red and her skin was pink so I though she was having some sort of reaction to something. I asked Paul about it and he said Natalie poked her in the eye again. Paul had heard Katelyn screaming and found her and Natalie sitting in a fort and Paul asked Natalie if she hurt Kate. Of course her response was "No" so then he asked why is she crying and Natalie answered "because I poked her in the eye". Because of all of this when Paul took Natalie to school he talked with her teacher and asked if Natalie had poked anyone in the eye and that she was doing it at home. The teacher said that Natalie was most polite kid she has in the class. She said Natalie always listen, never talks out of turn and always says please and thank you. Paul told the teacher that she must save all the other behavior for at home.