Explain to her that you in no way intended to hurt her or her daughter and tell her how you feel about her daughter. Explain to her that neither of you are little children anymore and can make your own decisions but do so nicely and respectfully as to make her see things from her point of view and listen listen listen! She will have things to say they might not all be nice but you need to listen to what she says and stay calm so that you can come to an agreement with her to show that you are both responsible and know what you are doing. Don't yell or get mad at her if she says something hurtful she is hurt as a parent right now because her little girl is growing up and if you stay calm and level headed it will show that you care and it will get more accomplished than yelling screaming and not listening. It will be difficult but try to see things from her point of view, you took her daughters innocence and she will never have that again and she just doesn't want her daughter to get hurt. Remember she is her child she will always be her baby girl.