YTA The worst part is you not being brave enough to just tell your daughter you don't love her if she doesn't got the same genetics as you. Continuing to be just normal with her brother is also so cruel.

You should ay for therapy for your daughter, she is the most punished person here for no fault of her own. Did you want to hurt your ex wife by this, so she has to tell your daughter and deal with the fallout? Even if she tells her abaut you not being the bio dad, what would that change about the parent-child bond from your daughters perspective?

Also what will this do to the sibling relationship, is your son already behaving differently towards her.

I get it if you can't be in contact with her for your own mental reasons and it's better to stay away than be awful to a child. But then you need to make a final decision and tell her what's going on and why and get her therapy so she hopefully will not develop huge problems later one.