not2cleverRed
Obvious Observer
Because, generally speaking, that's how it works in unmarried situations - both parents must give up their rights for a third-party adoption. You would be wise to speak with an attorney since your situation is different. (Adoption is rarely a DIY project...)
And you are unmarried lesbians.She had her there is no father because it was a donor
Get married. Then adopt.
I'd be more terrified about the limbo you'd be in if your partner of over 10 years died - because you are not the (legal) parent. I realize that marriage was not an option 10 years ago, but it is now, so get the piece of paper. (You don't need the party if you don't want it.)