Well perhaps prude isn't the accurate word here, but she's somewhat pure, at least with MC. Never allowing deep penetration, always demands the use of rubber and wants MC to be gentle, never a bit more passionate and rough sex, but if you play things so that she ends up hooking up with Beeman, then all that goes out the window, she'll do everything she didn't do with MC because suddenly she has no problem with any of that xD
But yeah, even a pure girl can become a bit naughty for a guy she really loves, you can be naughty and still be a good girl, you're just naughty with that sole person you love