But the biggest potential problem is that it could set up a competitive dynamic between the kids. DD is a big comparer, and gets exceedingly jealous easily. I'm worried she's either going to feel terrible when she finds out her scores are lower than her brother's (very likely that at least some will be, he's pretty high on the verbal ability), or that she will make him feel badly about the areas where his scores are lower (also likely, given that his processing speed is average, and I'm guessing hers would be at least high average -- she's quick). She will not be able to see the bigger picture that I see, or that other kids might: she's quick and funny and socially very astute, so even if she's not "gifted" on a numerical IQ scale, she's very smart and she's got a lot of other things to offer.
You may wish to share all these lovely things you've said with your daughter (ensuring she knows that she is quick and funny and socially very astute, she's very smart and she's got a lot of other things to offer). You may also wish to begin looking at books and resources such as Gifted Kid's Survival Guide and social thinking (perspective taking) to help assist you in coaching the development of your daughter's self-reflection on her interpersonal skills, as from your post it sounds as though some of her thought patterns are not serving her well.
Some may say that sibling rivalry is related to boundary issues; working on developing healthy boundaries may help head off potential sibling rivalry.
