I mean you could bring it up. Maybe after you guys just had sex or even better before, whenever you guys are just bs’ing with each other. First tell her to promise you that she won’t judge you or think different of you...make yourself kind of vulnerable and at her mercy. Then say something like “ can I ask you something babe? Is it weird that I got a little excited When we were talking in the car the other day.” And then gauge her reaction from there. More than likely it will go smooth, and the door will be even closer to opening and the subject can be brought up easier and easier. Plus she will appreciate your honesty... if she’s the type that values truth.