What to do when a friend of more than 10yrs played your back?

I'm single with son. I know this guy since 1985 but lost in touch in 1989.In late yr 1999, I meet him by chance. We kept in touch, exchange contact numbers. We went out for sightseeing, lunches and dinners together or at times with son also. All this brought us close to as a family. We even decided to get married with my son's approval. I shared this with a friend of more than 10 yrs about me falling in love with this man. He is someone who is special in all aspects of life. I even introduced my man to her. She exchange hp numbers with him and start cont contacting and smsing behind my back. My man told me about their calls and smsing but didn'tt even say a word about it, she even told my man not to tell me about on all the calls,lunches,dinners and even dating. When my man asked her for the reasons,her reply was that I'm a evil jealousy person who'll break their friendship. She's showing that she loves my man by buying expensive gifts,going to cly posh restaurants for lunches and dinners. She even brought him alin 4 or 5 stars hotels. All paid by her.Now my man & I are drifting apart,gg & quarrelling for no rhyme & reasons. When I confront her on stabbing my back. She denied all & even accused me for trying to breakup her happy married life. She is married to a businessman & has a child too. Its hurting me greatly cos after years of being a single & lonely,I've found a man who shares alot of similarities in life with me. When he is around, the house & our lives are filled with his jokes & laughters. We were very happy with him. Now there are gaps in all our conversations. At times,no calls from him for days. Not sure what to do. I'm at loss, stressed out & am depressed now. !!!