HK: Some of my post-HS social experiences were similar to your DD's, even though I was not accelerated. I graduated at 17, but then I worked for a year before joining the navy, so I was very age-normal for my cohort.
And still, I found that "my people" were 3-5 years older than me, and those were the people I gravitated to (and who, in turn, gravitated to me). I got left out when they hit the bars stateside (not a problem overseas), and my nickname was "Junior." I hit a social sweet spot when I turned 21, but slowly "my people" started moving on (enlistments ended, new duty stations, marriage), younger people came along, and I just didn't connect with them the same way, so I began to experience a different kind of social isolation.
So, being of normal age doesn't necessarily help a young gifted person socially.
