First of all, thanks for everyone's input on this one. As it turns out it pretty much took care of itself.
I verified that BF was ,in fact on the dating website. Then I posted a WTF on his facebok.he called and i confronted HIM with the info. Of course he denied everything. I made no threats or anything. Hung up amically.
Next am, He facebooks me and calls me to tell me he told my daughter.Now, I'm thinking , she will never speak to me again.
Next she calls, she is enroute to our home. Turns out, he did tell her, made all sorts of excuses ect. She had been doing her own sleuthing in the months prior and this did not come as a surprise to her.
He is in the process of moving out. My daughter and I are very close and thank goodness, this turned out ok. Especially that they did not marry and have kids, and then find out. Of course her heart is broken, but not as bad as I expected. She seems better every day.
For future reference, I will mind my own business and no more snooping. Lesson learned.
I want to wish all you ladies the best of luck and thanks for the advice, even if you were very tough on me!