Hi, non-nude here. There was a period of time when my chat was mostly non-sexual and questions like this would come off as rude or throw off the chat and I would ban. There is definitely a time and a place. I don't know what her chatroom is like, but most non-nudes (at least on MFC) try to have a fun chat with little sexual talk, it's more about the social atmosphere. I would start by purchasing PMing from her so you can message her privately FIRST to make sure she does that while also not interrupting her chat. If she's the type to not be sexual all the time politely let her know that you're pming her to ask about a certain fetish but would like to ask her when she's not engaging in her room or is in a more sexual state of mind. When you're ready to ask it's nice to ask what HER boundaries are first, then be very honest and blunt about what you would like (I'm assuming a private or a custom video?). If she says no, don't push it, thank her for her time, then enjoy her room for other things or move on. Don't be pushy if she says no, don't ask again later, and don't ask in her public chat.
These are just things I like personally. I'm about more open about sexual talk in my chat than I used to be, but if you come in and immediately say "HEY ARE YOU INTO SUCH-AND-SUCH, BB?" you'll probably get banned. Also if you come in and I'm in sweatpants, playing music, or doing something goofy then it's probably not the best time. Hope that helps, it's just my point of view and every girl is different.