Rogelio, this will work: the next time she does this, yell "STOP TOUCHING MY BODY" in a voice loud enough for everyone in the class to hear. Then, still in a loud voice, ask the teacher to have your seat moved away from this student. Everyone will be looking at her with strange looks on their faces. This will put an end to it. You have the right to not have anybody touch your body in any way without your consent. Your teacher will know this.