Sisters of the Moon Lyrics
As she walked in the room
Her black robes trailing
Sister of the moon
And a black widow spider makes
More sound than she
And black moons in those eyes of hers
Made more sense to me
Heavy persuasion
It was hard to breathe
She was dark at the top of the stairs
And she called to me
As friends often do
I cared not for love, nor money
I think she knew
The people, they love her
And still they are the most cruel
Be my sister, sister of the moon
Some call her sister of the moon
Some say illusions are her game
Wrap her in velvet
Does anyone, ah, know her name
When there is no choice
And we listen to their voices
Ignoring our own voice

I also think this is Stevie writing about herself. Like lots of artists, she had to come to grips with the gap between the stage persona she created, and the public's perception of that image. "The people, they love her / but still they're the most cruel" is the one line that sums up the psychology behind the song for me.
There was silly public speculation in the late 1970s that Stevie practiced witchcraft. (In case you weren't around at the time, some right-wing religious groups could get very scary with those kind of accusations on TV.) Stevie started wearing pastel colors instead of black, put her hair up in a bun, started dancing on stage instead of twirling (check out videos made during the TUSK tour) .... all to counter those silly accusations.
"Sisters" IS scary and gothic-sounding. The power chords are awesome, the closest FM ever came to heavy metal. Lindsay's guitar solo sounds like a screaming voice. Stevie's confronting the public rumors about her image, and the trouble they caused for her fans and herself. It's both a defense and a rallying cry - a self-parody and an anthem.

That's what I have just found at some Nick's site: About the Song About: A bad mood
A lyrically enigmatic Stevie contribution, with a guitar solo by Lindsey that’s reminiscent of “The Chain,” this was a surprise addition to the set on the band’s spectacularly successful 2014/15 reunion tour.
Stevie: “I honestly don’t know what the hell this song is about. I’ve been singing it on tour for the last two and a half years, and every time I’m thinking, What the hell is that? I think it was me putting up an alter ego or something, the dark lady in the corner, and there’s a Gemini twin thing. It wasn’t a love song; it wasn’t written about a man, or anything precious. It was just about a feeling I might have had over a couple days, going inward in my gnarly trollness. Makes no sense. Perfect for this record!”
But in another Interview she said that this song is also about the situation when she looked in the mirror and spotted herself as a very thin and almost dying person, here's a part of her comment: “I walked out in front of a mirror and looked at myself,” Nicks said during a 1979 radio interview with Jim Ladd. “And I was sick. I went, ‘Oh, poor sad little thing. She must be dying.'” Yeah, her both bad physical and mental conditions were because of hardship of touring and she even didn't sleep and eat much.

The black widow spider symbolizes feminine power, death, and destruction. It's a reminder to stay alert and avoid obstacles or threats. In shamanic ideology (at least from my lineage) black widows are protectors of the home and the evolving spirit; they are icons that depict the nature of deliberate and specialized attention to the finest details of life. So she’s basically writing about herself.

Gosh I have no idea what this song is really supposed to be about - except the literal interpretation of some gothic-type woman that Stevie is describing. Beautiful song though.

I can't say for sure...but watching Stevie perform this song drugged out of her mind makes me think this is about drug addiction.
This "sister of the moon" in the dark robes is cocaine (Stevie's drug of choice). The drug calls to her and Stevie cannot break free. "Illusions are her game," "so we make our choices when there is no choice..." Yeah, I'd almost bet money on this being about drugs.
I don't see any reason why something described as being in "dark robes" would be cocaine.
I don't see any reason why something described as being in "dark robes" would be cocaine.

I'm inclined to think Stevie Nicks is writing about her own witchy woman stage persona.

What a trippy song.....This Stevie singing about Stevie ...

I think this song is about a person looking at the darker side of themselves. I think its about the fight for it to prevail and ultimately it wins...

Witches