I'm sorry that happened to you. Maybe it's better not to be surrounded by a person that thinks rocks can help heal you?

Facebook makes it to easy to end friendships if it happened in real life there would be a lot more discussion and less friendships ended

It has been my experience having done all that stuff.......people who believe in something it. We are searching and when someone is harsh about ones belief it will cause one of two reactions.... A confident ignoring or a violent reaction such as what you experienced.
I love crystals for their beauty and presence but don't practise it as a belief system. She felt judged...her vulnerability was exposed. Call her patch it up.

I wouldn’t worry about it. No biggie, there’s 7 billion humans around here. I wouldn’t stress over loosing 1/7000000000th of anything.

A rose by any other name is still a rose.

Ya gotta take your own path regardless of who is with you or against you. A true friend would have said I'm okay with that and remain friends. Then again would a true friend have said anything? You win some and you lose some. It takes longer to lose some than others just as it takes longer to win some. Look at it as one part of your life that you just let go of because it no longer suited you because it was important enough for you to speak your mind and risk losing this person you considered your friend.

Beliefs, good or bad become part of a person's core values, therefore, to say that her beliefs are BS would have registered in her mind as a personal attack. When a lot of time is invested in any kind of belief so is a sense of personal identity.

Perhaps you could have been more tactful, but you were corrct in being truthful with the person.C
halk that one up to experience, but don't grieve over it.

Cognitive Dissonance is actually painful. After twenty years she could not think of you, or look at you and not question those belief which would cause Cog Dis, so she ended the relationship rahter than rethink an entire world view, just to reduce the pain.

Hard to assess without knowing how close you were, what you actually said, and what she actually said. Assuming you apologised for being thoughtless and not considering her feelings when posting it sounds churlish on her part to end a long active friendship. On the other hand if the only thing she has hear from you in 5 years is something undiplomatically negative I can understand why she would rather only talk to people who at least mix the positive with the negative.

Your story with its unfortunate ending reveals the weakness in her character and her values. I do not wish to denigrate astrology. Astrology has nothing to do with this. Perhaps it is her insecure ego that uses the things she believes in. Possibly she feels deep down that she needs these things to be a somebody. Perhaps, without intending, it was that facade you threatened.

It wasn't a friendship, it just seemed like one

She is probably defensive because of having to use her spirituality as an excuse to not be religious. She may feel persecuted and for you to stomp on her like that may have felt like a violent attack. Also as we grow we tend to weed out people who don't accept us, and you not accepting her beliefs may have felt like you not accepting her. Have you offered an apology? You could have just said you don't believe in that, instead of attacking her. Honestly I have had to defend my freedom from religion for most of my life, and if I want to believe in magic and someone tells me it's stupid I usually don't want to be around that person. P.s. I don't really believe in magic, I do believe in wonder and mystery though because no one really knows and there is more than what we can witness or comprehend, not saying she is right for believing in crystals, but she's not wrong and not hurting people like religions do.