We were like sisters and we never hide secrets from each other.
Do you think it was uncomfortable for her to tell you this secret?
No, she never judged anyone so I was very surprised by this
Good friends relieve stress, provide comfort and joy, and prevent loneliness and isolation. Sharing a secret takes the social stress away from hiding the secret from people we really don't want to reveal it to.
So it's bad because she was like a sister to me?
It is not bad at all! It is great to be able have someone who you can vent to and let your stress out. The more you hold onto stress the harder it is to be present with others.