You hit the nail on the head with this, mountainmom. She's definitely a "intuitive feeler" and has always been very attuned to people and emotions. As a baby (starting around 8/9 months old) when we were out & about, if she saw or heard other kids crying, she would get very upset and direct my attention to it, almost like she wanted ME to help them. That was one of my first indications that I was gonna be in WAY over my head with her!
Thanks everyone for your thoughts. I feel better about pursuing the testing, and will see what steps to take once that is done. All she's been doing so far in math is addition & subtraction facts, which are pretty boring and dry, so it's no surprise that she doesn't like that!