Hi Buzzy,
I'm going to try to be gentle, but also honest as I talk with you. I know you're going through a lot of pain right now, and I don't want to add to it. But rebuilding a Godly relationship with your daughter is going to take time... and honesty.
Family situations don't just happen. The situation you're talking about has been building up and developing for years. It will take time also to heal.
It sounds like you've been wandering back and forth in your relationship with your daughter, between accomodation and firmness. You allow her a boyfriend to try to please her, but it doesn't sound like you really talked about what was allowed or not allowed. Then there's movement to be firm again. Has this been the cycle?
Consider God's relationship with the Israelites. Does He sway back and forth in who He is, or is he the same yesterday, today and forever? (He 13:8)
God is also continuously clear with them on what is right, even when this goes against what the Israelites desire, and we see this over and over again as the Prophets call God's people to repentance.
Here are some thoughts;
1) Set just, simple and fair rules for your daughter. Communicate them to her clearly and kindly, and explain/discuss them with her so she understands them
2) Stick by your rules, though be slow to anger and abounding in love, as God is to us (Jonah 4:2)
Your daughter doesn't need another friend. She needs a mother. Even though she will complain about the rules, people and especially young people want stability in their lives.
God tells us he will "punish the children for the sin of the fathers to the third and fourth generation of those who hate me, but showing love to a thousand generations of those who love me and keep my commandments." (Ex 20:5-6).
We've all made mistakes with our children, and they will suffer for our sin... perhaps making the same mistakes we made, because despite our failings they still love us and want to be like us. But God's love is greater still, and will be with us if we love, trust and obey Him.