My response was mostly aimed at @mstomper who wondered whether there was a correlation there at all, considering he felt every single girl to be intimidating simply for being a girl.
True, @Nrdsb4, the OP asked for anecdotes - from people who “have experience with this kind of thing”! You say you don’t - and you say it’s not a given that smart people area cripplingly shy, socially awkward or considered intimidating, so I’m assuming you’re hinting you are none of these things either.
The OP says her daughter is confident and outgoing (and good looking and well liked etc), so the intimidation factor is what’s left to explain the otherwise inexplicable. Others have concurred that they have experienced it to be a factor. I know that people have treated me as if they have felt threatened by me from age 6 onwards. I have had to consciously work against that. Thats my experience with this kind of thing, necessarily an anecdote, too.
To help the OP, what did you think made the difference for you, since it is clearly, not about shyness, awkwardness or other perceived social “deficits” for her daughter?