3yr old missing father

My DDs father and I haven't been together her who life so she has never known of us being together or living in a home with a mom and dad. She goes to her fathers one week a month because he lives about 7 hours away. Lately DD has been talking about her dad more asking if he can come to visit our house and has even asked if we can live with him. I don't know if this is all her doing or if its her dad planting the seeds because he to this day pines over me and asks for another chance.Either way it does make me sad for DD because I feel she is feeling like she is missing something or not getting the "full affect" family wise. I have always just explained to her that daddy lives at his house and mommy lives at ours and that's why she goes to visit daddy. She loves us both very much and right now I think she is wondering why it has to be one or the other and it's hard on her.i can't help but have a sense of guilt cloud over me because of it.