He's the father. Not much you can do about it. Make sure the kid knows who mom is and that's that. Other females will be in your daughters life the second you put her in daycare, or in school, or anywhere really. There will be other women in her life the second you need a babysitter, a housekeeper, or even as soon as your female friends come over. You can't protect her from other women, whether they are dating her father or not. Stop being silly.