I think it was more the latter. It's been a while since I saw the Carmilla video, but I remember her filming with a dog handler present. They were in a warehouse or something like that for that one. Even if beast porn is her fetish, they obviously didn't go there to do anything more than pose suggestively for the camera. The dog unexpectedly getting aroused by sniffing her (didn't it try to mount her too?) would still catch her by surprise. She may have just been surprised and tried to laugh it off with the others who were there for the shoot. She could have been into it deep down afterwards, but your guess is as good as mine. Maybe she's had fantasies about it, but like most people into more extreme forms of porn, you never consider acting on it.
Even when she "caresses"/tickles the horse's balls, it still looks more like she's just brushing fingers against them than really going for it. I'd even say there's hesitation or her being very careful when she does it. She’s testing the line rather than crossing it. It's still very uncharted and uneasy territory for her, regardless of how deep her fetish might go. At the end of the day, they were just there to shoot suggestive beast stuff.