Aggressive tendencies in 3 year olds are still within the normal range -  the child doesn't need medication (but a parent might want some to help cope with the toddler!). If the child is still very aggressive at age 6 or more, you could look into an assessment at that time. Meanwhile, you can help by gently redirecting her. You can say, "Please give so and so the toy now - it's his turn to play with it." When she has a fit, you should try and remain very calm, quiet and in-control - your model will help your child. You can name her feelings, "It's hard to share your toy. You want to keep it." Then add, "You'll have your turn again soon." Just let her cry - the noise is disturbing but harmless. When she sees over and over again that no one is flustered or panicked by her hysteria, it will help her eventually keep her cool as well. Good luck!
Sarah Chana