You should ask your pediatrician about giving Melatonin. Pedi will probably recommend Benedryl, which I absolutely detest, because I think it makes my daughter behave horribly for several days after she stops taking it.
Your 9 year old should be able to take Melatonin, but I would start out with the lowest dose possible. I do believe they make 1 mg. tabs. I have 3 mg. tabs and cut them in half to start with my daughter. If that doesn't help, I'll give her the other half.
I don't know what GABA is. If it is what I think it is, I think it is just brand name for Omega fatty acids, no? Omega fatty acids are good for everyone to take. You can get ripped off online with some of them, so if you have a good health food store, you can check with them. You can also check Amazon (through the site to help support our site) for Omega 3 6 9. They have all three Omega acids and are really the best for targeting some of the issues you are referring to.
Lastly, no one in your area will see her until she's six? Call your local children's hospital and ask for a mutli-disciplinary evaluation or write a letter to your school district and ask for the evaluation. Check out the spec. ed forum for more info on that.