Welcome! We used the Hoagie's list, and found an excellent tester: http://www.hoagiesgifted.org/psychologists.htm. Your DD sounds a bit like mine, btw...she is very, very self-directed, which can sometimes border on uncooperative. Trying to work with the school to find good teacher fit before the year starts has helped with this.

We waited to test until we needed it for a program. My DC were tested between ages 6-8, and the results did match what I see in real life.

Best wishes to you and your DD!