Nutmeg, what jumped out of me from your original post was this -- you said she was mature, with a wicked sense of humor, and a great vocabulary. One thing I have learned from hanging out on this board is, you've seen one gifted kid, you've seen one gifted kid. Frequently, younger sibs present as less "typically" gifted. You may not think she seems gifted, but I rather think she might be. Mature, sense of humor, good vocabulary... If it were me, I would want to test.
Just jumping in to say I agree with this. My two oldest are gifted and it was pretty obvious. We thought the third was bright but not gifted and had her tested just to make sure that was right. Nope - all three have the same GAI. Also the same processing speed - which was described by the psychiatrist who administered the tests as "slow as molasses."
I would have her tested. Very perceptive and mature, with a wicked sense of humor and a good vocabulary are clues I think.
