Grabbed a lady's butt at work and now she is trying to black mail me?

A few weeks ago I patted this lady on the butt at my office. She is a temp secretary I hired through a staffing agency. Okay, the project she was working is completed and I no longer need her. She has requested to work her permanently, but I told her it is not possible now. She says she may get an attorney and file a sexual harassment suit against me. However, she says she is unsure what she will do, but really hopes I can bring her on as a full-time employee. Even though, she hasn't said directly to me what she is doing, it is pretty obvious. Basically, I have to give her a job or she is going to file a law suit against me and say I am letting her go because she declined my sexual advances. They were not sexual advances, it was a one time thing and I apologized afterwords and said I was just kidding around and at the time she just laughed it off. If I can somehow prove she is black mailing me, can it cancel out her sexual harassment lawsuit? I mean, what I am saying is this, can her law suit no longer be considered if she is using it to gain leverage against me unlawfully?