Wasn't it implied that without Equius Nepeta would have a high chance of going full "apex purredator" since she doesn't care all that much for all that society stuff and civilization? Or was it some weird fanon that I accidentally mistook for canon?

It may have been fanon, she does care enough about her furriends that I don’t think she’d ever go full predator- That being said, she IS a Rogue. She’s very much an outlaw with a closed group of friends, so while not full predator, she’d likely be more predatory and wild without him.

In a way, though, you could kind of see her as the opposite than the Disciple if you want to run with the idea she’d be a lot more savage without Equius and her friends. The Disciple lost the Sufferer, and then, spared by Darkleer, she ran away and lived her entire life in savage isolation writing his teachings on a wall. Meanwhile, Nepeta would be a wild predatory huntress, but with Equius’ aid she’s kept a bit more grounded, and ends up not being able to confess her feelings to Karkat.