Hi Lars.
Try to undo whatever that other person did.
Explain to her that you do, indeed, like her, but that you feel very uncomfortable about the way that that lad told her; that you hope that she didn't feel that you might be behind it, because you weren't, but, if she is willing, you would lke to go out with here ~ perhaps to the cinema, or bowling, or something like that ~ or even to the library or to one of your homes to do homework together.
Good luck.