"All I've wished ever since I first met her is that things could be different and that I could have actually given birth to her, fed her, changed her, watch her speak her first words, helped her take her first steps... Everytime she has had any kind of milestone while I've known her, it always reminds me of what I missed when she was a baby because I wasn't in the picture."
That (above, what you wrote yourself) is what you tell her over and over. You do not let her breastfeed.
The reality of the situation is that she was born to her own mother, which, in fact, makes her very very special. You really wouldn't want to change a thing about her.
At 9, she needs to learn that just because we wish something was different/had been different, doesn't mean that we can make it so.
You got to start your relationship with her when she was older. Even if you had been around as a baby, you couldn't have breasfed her. She wouldn't be the same little girl that you and her daddy love so much if you had been able to, because she would have been born to you.
Definitely talk with her counselor, but it's time to teach her that we can't have everything the way we want and that sometimes life isn't fair. Let her know that it hurts you, too, that she's not biologically yours because you feel so strongly that she should be. Let her know your hurt and pain over it, and let her learn to deal with disappointment.
It's not the same disappointment that she has from her bio mom, but she will be disappointed by others in her life, too. Teach her that it doesn't mean anything changes. Just that we can't always have what we want, even when we want it really really badly.