The singer/songwriter wrote a series of Instagram stories that have since been deleted - according to Buzzfeed.
"Just so you know...this is a mink. You b*****s getting mink lashes and mink slippers disgust me lol," the star wrote. "Where yo heart at?"
The comment follows a video of a mink hiding in a tree stump, which went viral on Twitter.
This isn't the first time Billie has spoken up about animal-rights and veganism. Earlier this year, the 17-year-old slammed the meat and dairy industries for 'torturing animals'.
"I keep my mouth shut most of the time about this because I believe everyone should do eat and say whatever they want..and I don't feel the need to shove what I believe in, in anyone's face," she wrote on Instagram, following a major dairy industry expose.
"But man.. if you can watch the videos that I just posted and not give a f*ck that it's YOU contributing by LITERALLY EATING the creatures that are being fully tortured just for your pleasure, I feel sorry for you.
"I understand that meat tastes good and I know you think you're just one person and it 'won't change anything if you stop' but that's ignorant and stupid. If you have half a brain, you should know 'one person' adds up. Be smarter."