Agreed. I think most of what you describe there is pretty common, WBGTE. I know we had the same problem with underestimating DS7's LOG because most of the people we know are MG or above. I thought he was MG, most of the kids in his playgroup were ND, and there were one or two who were "a bit slow." As it happened, DS was HG+, the majority of the kids were MG-HG, and the "slow" kids were ND. Oops!
When I got my wake-up call, I was looking at his out-of-level achievement test scores, and they were 1-2 SDs higher than I expected them to be. So I had a moment of "Wow! Yippee!

" followed by a moment of "Holy %$#&! Now what?!?

" The GT coordinator was talking to me, but I didn't hear a word she said. She sounded like the teacher in "Peanuts." I was too freaked out for anything else to register! No tears, but lots of mixed emotions!
My advice: wait until she a bit older and have her tested. If her maturity level, your gut and the test results make you think that she's ready for early K, then go for it!