I'll bite, though my own DD is only just 4.
a) My DD's reading progress has been much more up & down than your DD's. She began reading at 2, but didn't progress to sounding out unfamiliar words until about the time she turned 3. Then, she went up a grade level about every two months until she hit 4th grade (about the time she turned 3 1/2). That was pretty shocking.
She's a big reader, but still not into chapter books--the interest just isn't there. I say that her progress has slowed, but the truth is that it's not her ability that now limits her; I'm sure she can decode on at least a 6th grade level. So...my answer would be who knows? But really, once a child is a fluent reader, education becomes much more about content than about the actual reading. I wouldn't expect hugely-above-level reading ability to _necessarily_ translate into a need for hugely-above-level curriculum.
b) DD is also similar here. She does basic addition and subtraction, but she has a few strategies besides finger counting (and can do some simple math in her head). I don't plan on doing a curriculum. She's taught herself to count forwards & backwards, etc., and has great number sense, so I am very confident that she'll figure it out on her own.
c) DD has no trouble making friends thus far. Does your DD? FWIW, I was HG+ as a kid, and I didn't have any trouble making friends. I don't think it's inevitable. As far as connecting her with other kids at her ability level is concerned...well, it's not super likely to happen.
We hope that DD will be able to join DYS when she's older for that reason. If not, we'll just sign her up for gifted programs and hope she can meet a few peers.
d) Nope. I've ranted plenty about this elsewhere, but IMO giftedness is not one of the areas of a pediatrician's expertise. So if they give you advice it is not more likely to be correct than the advice of any other reasonably intelligent, but ignorant, person.
