What to do with my best friend?

Sorry if it's a bit long but some help would be great! So I fell hard for my best friend about a year ago,were both girls, and after telling her how I felt we still stayed close, it affected us though till this day. After telling her, it was an awkward topic to talk about since she had made it clear that she only saw me as her best friend and nothing more. We both have our jealously issues, she didn't want me to be friends with other people, especially not friends i would talk to about her. And me when she talked about guys she had prior flings with. we struggled but continued as friends, deep down i still had high hopes that we would one day be more then friends ( since we spoon, see each other naked and were are extremely open and comfortable with each other) But just recently she has started seeing this guy she meet (her first "boyfriend") and my jealousy has kicked up a notch. From what i know he's a good guy but everyone knows its hard to see someone you previously cared a lot about with someone else. I've never had such a good friend that i would do anything for but even though im extremely happy for her it hurts me to see her with him. So we've decided that for now we will go our separate ways, this way i can learn to deal with the fact that she isn't mine and for her to see where her new relationship goes. Instantly i regretted making this decision because i cant imagine my life without my best friend but this way we can both be happy. Am i right to let her go and be happy with him even though i lose her, or should i just deal with the pain of seeing them together just to have her in my life? Or any the suggestions that could make me feel better right now. Thanks!