If this individual truly threw some keys at another employee, thereby posing the risk of injury to whomever she targeted, the incident should be reported to management immediately. This is typically grounds for termination. However, if she shoved the keys across a table or engaged in a similarly inappropriate but somewhat benign act of aggression, there are some other steps to consider.
It’s important for you and your fellow employees to be certain that there is nothing you are doing that could be generating this type of behavior from her. Sometimes current employees form a clique that is not particularly receptive or open to new employees, and the result is that new employees push back and also complain to management.
If you are certain that the actions of this new employee are reflective of whatever baggage she brings onto the job, then it is time for two possible discussions. First, you and some of your associates should meet with her to discuss her actions. Importantly all of your comments should focus on her behavior, and not on her personality. Reemphasize your willingness to work with her and help facilitate her transition to the job. If she continues to engage in inappropriate behaviors, the key step (so to speak) is for you and your associates to then discuss the situation with your manager. | 
