How shall I handle my promiscuous daughter?

My daughter is 15, and we have talked together about and kissing. Last year, she promised me that she won't be doing any of it until marriage. She started dating this summer (I think she is too young), and I spotted them kissing yesterday. Not just kissing, but snogging! She was touching him all over. I have given her the freedom to see her boyfriend between 3pm and 7pm, but she is not allowed to have or snog. I can not trust my daughter anymore, and I ed her yesterday for her promiscuous behaviour. I don't want my daughter to be promiscuous. I don't want her to have before she is married. I want it to be special for her and I don't want her to be lured to bed by boys who will only dump her. Do you have any advices?