J.P.
Hi--
I have two, so I can't speak from the Mom perspective, but I am an only child, so I can speak from there. I liked being an only. Having a new sibling at ten would've messed with me because I would not have wanted to share my Mom. I got lots of space and lots of time and I liked it. As for having siblings, I sorta just created family out of my friends. I have great girlfriends who fill that place for me, and I don't feel as if I am missing out. It sounds as if you are happy being Mom to an only, and when Momma is happy, then so is everyone else. I don't think you need to worry about it anymore. Everyone has different families and all variations have advantages and drawbacks. You're a good Mom and you're daughter is lucky to have you!
J.