She is going to leave me

My daughter is 5 and she tells me all the time how much she misses her father and wants to go to his house. His house has no structure and no rules to follow....so of course she wants to be at his house. Why do I have to be the bad parent for making her follow rules and to become a good person? I do not want her to chose him over me. This is already having an affect on me. What do I do? I love her so much and cannot live without her being with me.