DD13 DYS has always been the child in our family who just screamed (sometimes literally) that things were not working right at school. DD14 is our compliant, people pleasing, incredibly studious child. 2 very different kids. DD13 grade skipped into DD14's grade a few years ago, and DD14 has mixed feelings about this especially when she gets the questions, "What, is your sister so smart?" or "Are you not as smart?"" or other versions of those. She ultimately has taken away the idea that she is "not smart." It's very painful. We process this with her, but she still feels negative about her intellect. BTW, the girls are not genetically related so a similar IQ would not apply.

The question I have pondered more lately: are we underestimating DD14? Have we not advocated enough for her? The girls are at a fairly rigorous private high school where DD14 gets 99's and 100's. DD13 gets 95's -97's. Their MAP scores were very similar with DD14 getting higher math scores (she loves math), and DD13 doing better in LA. The big difference between the 2 were the Lexile scores with DD13 getting 200 points higher. I wonder though - DD14 works so hard for those scores. She studies much longer than we (or her teachers) wish for her. DD13 never studies. She doesn't have to. DD14 feels like a moderately gifted high achieving child to DD13's highly gifted incredibly research driven (if it's interesting to her) kid. I have this feeling that if DD14 received higher level work she would become more stressed. I am begging the school to challenge DD13. I believe I am answering my own question, but I still wonder.

Personally I would have the elder sibling tested. Higher IQ is not always better, there is an optimal intelligence range.
- This article mentions 125-155 as being the "socially optimal range." Note that was in 1926 when the ranges were broader.
- This article mentions 120-125 as an optimal IQ range for leadership. Related thread here.

I would help her understand where her IQ is on the IQ curve, and the relative rarity of her IQ score.

I would help her work on addressing any self-doubt or lack of confidence about her intelligence with facts and logic, rather than relying solely on emotions and opinions.

People have different physical characteristics, including their brains. There is an art to accepting ourselves and also accepting others.

It is possible than any child may have both high IQ and a learning disability or learning difference which may tend to mask the high IQ. Compensating for this second exceptionality (2e) may divert a lot of a person's time/effort. For example, studying and/or completing homework may take longer.