You know her and how she will react definately tell her on her own though and say that you don't want it to ruin your friendship because you understand it willbe very hard for her. Doesn't always work the response I got was "I'm jealous, I really hate you right now and I want you to get out" and has only spoken to me once since. Just try to be understanding and not take it personally if they don't react too well to your happy news.