I'm not sure, but I think this may be at least the third thread that you've posted about this. It's obviously a huge issue for you, but I'm not sure if it really is the disaster you feel it is. I really agree with what you say that people shouldn't listen to playground opinions though.
If your dd is happy and settled and likes the school she's at then that's a good thing - it would be different if she was unhappy. It sounds as if you're in the grip of some awfully catastrophic thinking and you're ruminating a lot (in the depressive sense) on your decision. That must feel really crappy and miserable, I know, but you're not going to resolve it by even more thinking and what-ifing.
I do know how you feel - I went along with one subject decision for a dc then wished I hadn't. I sometimes ruminate and catastrophize too and it can feel impossible to let go of it, the worry and regret niggling and prodding at me. But it's done, it's finished, and there's no point me thinking about it any more.
Like your situation it's really not a disaster, either - just a regret. The outcome could still turn out to be great and I'm sure that's true of your dd's school choice, too, especially if she's enjoying being there and doesn't want to move. Do try and focus on that good possibility, nothing's black and white and there's an awful lot of grass is greener thinking going on when we dwell on things we regret. If you actually did have the thing you want, you could easily be worrying the other way and no better off.