Insulting classmate

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I am having a problem with my classmate. We had to do a presentation together, there was three of us. I did almost all the research, as well as the other girl. and the third girl took the reserach and decided to do the powerpoint presentation. After the presentation the girl who did the research and i left and went to the washroom. During this time the girl who had done the powerpoint siad to the teacher that she can probably guess who did all the work, implying that she had done everything adn we had not done anything. So one of the classmates told me what she said and I confronted her and she is now lying about it. I dont know what I can do at this time about this. Does anyone have any ideas or had a similar problem