"But you know, I always felt like I was that person that no one gave a s**t about due to what people said to me online.
"It was absolutely unbearable. And that's why I write, 'My sister's like sunshine, bringing good light wherever she'll go/and I was born to rain clouds, blessed in her shadows.' Because, that's why everybody always says to me, that no matter what, I was going to be in that shadow."
Noah admitted she "always believed" she'd be in Miley's shadow and her worries had been a "big part" of her life for years.
She continued: "That was something I heard my whole life, every single day, my whole life. It was either that or that I wasn't enough in some way, whether it was the way I look or the way I am. Like I said the other day, sometimes I feel like I don't even breathe right sometimes.
"Basically, that is what the song is about, and I just wanted to open up about that once and for all, because that's been a big part of my life, and I probably won't talk about it anymore. I just wanted to put it out.
And the brunette beauty finds it hard to sing the song.
She admitted: "Everybody always says you're giving the people power by seeing it, but I can't control seeing it.
"You guys are young, you know the internet. It's been really tough on me, so that song is just pretty tough to get through."
