DD (11) just started todayand I know exactly how you feel
She wrote me a note in code (presumably so that DH and sibs couldn't read it?) and when I asked her if she had everything under control she assured me she did. We giggled in the kitchen about how our hormones would make her dad miserable and had ice cream I am so proud that she is handling it so well (she tends to be squeamish about blood) and yet I'm all misty about my baby growing up
I plan on buying her some jewelery to commemorate the occasion and leaving it at that. She seems not to want to make a big deal of it.