My DD was 10, almost 11, and yes it can be very confronting to realise that your daughter is growing up.
You sound like you have done a great job preparing her for this, no matter that you weren't there with her, the important thing is that she was prepared & didn't freak out.
I think that realising that she is entering a new phase of her life can be hard to deal with, it's real concrete evidence that she is growing up...as you said, she can make babies now...and yet she is too young for that! she is in that strange place where she is still a child but growing into an adult.
If puberty marked a difficult time in your life it could be that you are afraid of what this will bring for her? Trust in what you have given her so far, and that her life journey will be hers... she sounds very 'together' thanks to you, I'm sure she will be fine
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