IMHO, it's obvious -- to me -- that OP's change of story was just that: a change of her "story," and likely with the intent of avoiding further discussion with us about that "story."
there was no change in the story.
child has always known that there is a person out there who "physically" contributed to her existence. that person is indeed her legal father.
child knows step dad to be the only "daddy" in her life.
you need to be more than a sperm donor to be called a father.
sorry if i can't be more clear. one sperm cell does not make you a "daddy".
"daddy s" go to school plays, tough out the freezing cold weather to watch you cheer a football game, stay home from work to take care of you when you are sick and so on. they are involved in your life. they don't just show up one day and say "hey, i'm your real dad, nice to finally meet you"
don't know how else to explain it....
what you think was a change in my story was just me trying to be more clear