Two-year-olds often hit themselves due to frustration, and you needn't worry about that. But be sure to take decisive action if your daughter is in any way aggressive toward you. Talking to her will not be particulalrly helpful. You have to discipline her. If she is aggressive, give her a time out (sitting in a chair for a few minutes quietly) immediately. All yuo have to say is "No hitting" (or whatever the behavior is). It's fine to say that hitting hurts, but all by itself that will not result in her changing her behavior.