Dude, I haven't been there yet, but I know I will be at some point.
When my daughter says something like that to me, I'll tell her to come over, give her a biiiiigggggggggggggggggg hug, and say 'Yeah, you have another person in your life that loves you. Its a good thing. But you know that I will always be your dad, right?'
Then excuse myself to the bathroom and cry.
It sucks, but ya gotta try and look at the positives for her. She's taking her cues from you. If you're sad (in front of her), she's gonna be sad. If you put on your game face, and trudge through the < feces >, showing how life is good, she's gonna take it that life is good.
It sucks that we have to deceive our kids sometimes, but we need to make sure they grow up well-adjusted and happy.
Now, go on a bar-crawl with your friends this weekend, just to forget about life for a while.
Audaces fortuna iuvat.
The meaning of life is Happiness. What makes you happy? - Dalai Lama
For a more peaceful life, live the serenity prayer.