Daughter having bipolar meltdowns?

My daughter is 18 years old and has only been recently diagnosed with Bipolar Disorder. She is in her senior year of high school right now and really struggling with her moods as well as her temper. She has only thrown very few of these bipolar rages, but recently, she has been having them a few times a week for hour on end. They have also become more intense and violent. I am almost positive that this is result of her not taking her medication, and I am not sure if I should have her hospitalized or not. My question is, how can I help her calm herself down? She is more violent during her meltdowns now and I honeslty have no idea what to do. Does anyone out there have experience dealing with this? If so, what steps do you follow?