Your cat is exhibiting normal play behavior. The problem is that, as with most cat owners, you are not giving them enough stimulation daily. Toys are an excellent way to combat this, try getting a few different types (laser light, feathers) and play with them at least once a day. Not only are you socializing with your animal but you are giving them exercise and the ability to let out their play behavior, even more with the age your cat is. Also, negative reinforcement does not work on cats, only positive. Reward her when she does what you want her to do.
-Cat owner for 14 years, my current cat started out the same way as yours and she still even beyond two years exhibits play behavior but no longer attacks anyone. Also if you have the time and are interested in learning about cats, the show My Cat From Hell features many different problems of cats and specialist who fixes them.