I have an ex gf that used to say that she liked to fantasize about monsters, like werewolfs. And, in response, I always joked saying "oh, so you're into zoo?", but she denied.
Until one day she responded that she had already watched a zoo video, but told me as something she did only once and she didn't make clear if she had liked it or not.
So, one day, i told her that after our conversation, I, moved by curiosity, went to watch a zoo video and actually liked it. We were so into creampies, so I told her that I liked the video because of the huge amount of cum that came out of the girl from the video I saw. She was interested, asked me to send her the video which I did and she told me she liked it too, but it looked like she wasn't comfortable speaking about it, so I didn't went further with the conversation.
Next time we talked about it, I used the same strategy: told her about a pig video and how it was one of the best creampies i had ever saw. But, this time, instead of asking me for the link, she just said "if you continue to watch this kind of stuff, you'll end up liking it and becoming addicted to it." So, yeah, after this, i never touched the subject with her anymore.
But I really think that, maybe, she would want to try something like this. Sometimes i suspected that she was into very "non-conventional" stuff. But she never opened up, despite my receptiveness.
Now I'm dating a vegan girl that definitely would consider bestiality a kind of animal abuse. So I'll never say anything about it with her.