Had a young man of 17 call me up a few years back. He was a good christian boy, and was a little disturbed.
The boy had three contenders for "DAD" to think about. All I could tell him was that the man who took of his time, treasure, and love to raise him was his "DAD".
If you're showing that kid the time, and love to raise her right, and take her shooting, the conventional titles (like "stepkid, stepdad") mean nothing. You're her dad, and she's your kid. End of story. She may have another dad out there, and if he's appropriately involved, it's only right of her to show him love and respect. But she's growing up with you, and she'll remember you as dad too. Not stepdad, just dad.
And way to go, dad.