Increased aggressive behavior

Hi, my daughter Kayli is 6, with a severe developmental delay and brain damage. She is developmentally at about 1 year old, and also is severely visually impaired. I have noticed along with her special education teacher that she is becoming increasingly aggressive towards other people. She has always had an "attitude" and started striking out at other people when she was about 1 year old. Generally it was always her father and I that got the most of it. Now she is striking out at other kids at school and her 2 year old cousin, she hits, kicks and head butts when ever she feels like her space is overtaken or she is being disciplined for negative behavior. (discipline for her is generally a firm No or Time Out space) she is going to have a little brother in about 3 weeks and I am really worried about how that is going to affect her. And also worried that if she struck out at him she might seriously hurt him. She doesn't talk so she doesn't have any way to communicate with us other than whining or screaming or hitting. she is currently on anti seizure medication and her old neurologist said in the past that if she continued to get worse with her behavior he could increase her dose to help with it. well now we moved 2000 miles away from him and going to see a new neurologist next week and I would just like to hear from other parents that may have gone the way of medication for behavior issues, and how their kids personalities were affected by it. Or anyone who might be going through similar problems. Thank you!
Robyn