Im in love with my really good friend but she has a boyfriend. What should I do?

I am in love with this girl I have been really good friends with for about three years. We hang out quite a bit and she knows that I am interested in her but at the time she did not want to be in a relationship. She was having some troubles with an ex and I was there the whole way to help her through it and in the midst of that I told her how I felt, she said that she was glad to have someone like me to be there for her but she didn't want to be in a relationship at that time which I completely understood so I continued to be there for her as a best friend and did not push her with my feelings. But recently she began going out with this other guy, but she asked me if it was alright if she began dating him because she values my feelings. I told her that she should do whatever makes her happy and she began dating him. I have been trying to not think about her but I can't stop thinking about her and I do not know how much longer I can go without telling her how much I love her. So, I guess I'm asking how should I approach this. Should I come out and tell her, should I wait to see what happens, or should I try to get over her. Please help I truly love this girl and would do anything for her.