You've received great advice above. I fall in the camp of thinking it's a good idea to test - the testing will give you *information*, and no matter what the actual IQ # that comes out of the testing, you'll come away with a good sense of her strengths/weaknesses and that's useful info no matter how smart or not-so-smart a child might happen to be - and it might be *especially* useful for a child who is clearly not happy in school.
Re the sibling rivalry, fwiw, I have an EG ds and one of my dds has a significantly lower IQ score. The thing is - my dd is *still* subject accelerated and very successful at school. She's an incredibly motivated child and while she might not have the high-level abilities of her brother, and she most likely won't get an SAT score in the same ionisphere he *might* get someday, she is a very happy kid with a lot of her own individual achievements and interests. She's asked me once what her IQ testing numbers were, and the question was specifically in relation to her brother's IQ . I didn't tell her for a very *very* simple reason - if I told her what it was, I think she would take it to mean she couldn't achieve as highly as she is. So instead I simply told her, no, it's not as high as your brothers, but look at all the things you are capable of and have done. I do truly believe she's a really smart girl - not because of her IQ score or in spite of it but because I've spent time talking to her, seeing how she approaches projects at school, seeing how she is passionate about subjects she's interested in, and seeing the high goals she sets for herself.
It's really easy when following these boards and when parenting an HG/+ child to start to think that a lower IQ is something that isn't a good thing - but really, ultimately at the end of the day, it's who we are inside that counts and there are still a lot lot *lot* of smarts inside kids who aren't profoundly gifted, or even moderately gifted.
That said, I wouldn't be one bit surprised if you ended up finding your dd is as gifted or possibly even more so than your ds - lots of kids don't scream "gifted" at the top of their lungs for the world to hear, especially if they are 2e. For that reason alone, combined with the fact that she is complaining about school, I'd test.
Best wishes,
polarbear
