It could...or not. At this age, I would not place too much weight on standardized testing of any kind, either individual, or--like the CogAT--group. I would begin, instead, from the observations you and her teachers have of her. Incomplete hand dominance is not all that unusual at five or six years old. Academically she is ahead, and apparently happy in school. The social lags could have many different causes, but my first thought would be her history of speech delays, and possible lingering effects in language.
If you are concerned for concrete reasons other than her CogAT scores, I would request an evaluation, listing the specific concerns you have (e.g., social development, sensory defensiveness, history of speech delays). When was she discontinued from speech? Do you have a good relationship with her speech therapist? That would be another resource, who knows your DD well, who could give you some input on whether any of these concerns are developmentally significant.
If your only substantive cause for concern is the CogAT scores, watchful waiting may be sufficient. Children test poorly for many different reasons, especially at this very young age. And their development also takes place unevenly. Finally, the CogAT can show quite a bit of variability from year to year. Not a reason to panic, in other words, but a good opportunity for some objective reflection on her development.
