I trusted her!* xxxx?

This does happen and you are so right to be upset. Your friend has been awful. However, I believe that if you enjoy her company and she is a good mate in every other respect, then keep the friendship but don't share any more personal secrets! You should have the conversation with her too. Explain that you still like her but you wont be telling her anything else so personal again for a long time. I think this will give her the chance to review her attitude and maybe learn that when someone asks for confidentiality, then she needs to abide by that and if she can't, make it clear to the person who is telling, that she cannot be trusted or for conscience sake would rather not be told. Its a question of maturity in the end. She has been a silly pleb probably out of jealousy but give her a chance to redeem herself. We all make bad mistakes but deserve second chances.