The 20-year-old singer broke down in tears as she admitted she had always felt no one ''gave a s**t'' about her because she was just the 'Wrecking Ball' hitmaker's younger sister.
Discussing the lyrics to 'Young & Sad', which features on her new EP 'The End of Everything', Noah said on Instagram Live: ''I think just the message in the second verse, being born in the family I was in, everyone gave me such a hard time for having a hard time being Miley's little sister.
''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.''
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