S.B.
I think it is great that your daughter confided in you! Great job! I believe not telling your husband is wrong however. I am sure this is why you are in knots over it. On one hand, if you tell your daughter that you will tell her father, she may not trust you anymore and will keep her thoughts to herself. But on the other hand, children grow up and move away and the person you are left with is your spouse. Any marriage counselor worth their salt will tell you that the marriage comes first. Sit your daughter down, hug her and let her know that you are so grateful to her for sharing with you but say you are uncomfortable with keeping this information from her father. Explain to her how you feel being married to your husband and hopefully she will come to understand that the bond you two have is something more than just sex or a piece of paper. You could reassure her that much like you, her father will not judge her and will remain calm. He will also be thankful for knowing what is going on under his own roof.
I wish you the best of luck!
Blessings!