I'm sure there would be nothing wrong with bringing up the subject of wearing "protection". And as far as her being AB, or DL, who knows? But, could it be more of you wanting it to be something like that, and reading it into what she says. Sometimes we want to hear that from other people, but it's not necessarily so.
If you don't want to alienate her, be careful here!
As far as my similar experience. The only one I can remember, is way back to when I was a kid. I was maybe 12, and my cousin was over my house. We were playing around, and trying to think of something to do. Don't know why, but I decided to kinda test the waters. I said to him, "hey want to wear diapers"? In a joking manner. He smiled, laughed, and said yeah, then garbed a plastic garbage bag that had been sitting there. He quickly wrapped it under and up his legs, while still laughing, we both did. Unfortunately, his mom called out for him right then, they had to leave! He pulled off the makeshift diaper, and yelled out, "be right there". Soon after that he moved, and we saw much less of each other. It never came up again, even when I saw him later. I never got to really see if he could have been a DL.