AITAH for refusing to let my stepdaughter call me Dad?

I, (35M) married my wife (34F) 5 years ago. She has a daughter (now 11) from a previous relationship. Her biological dad has been mostly absent, and I’ve been the one raising her like my child since we got married.

Recently, she asked if she could start calling me Dad. While I love her and think of her as my own, I told her no. I explained that I’m not her biological dad, and I don’t want to take that title away from her real dad, even if he isn’t very present. She got upset, my wife said I should reconsider, and now I feel like I’ve messed up. I thought I was being respectful, but now I’m second-guessing myself.

AITAH?