Rose knows there's a code to these things. Though her life detached from the brutal training of her father has led her more freedoms, more notably a nice warm body in her bed, it shouldn't be that of a hero.
The very prospect makes her shudder. But out of that pesky costume, you're divine. She feels her blood boiling at the mere thought of you, and if she can't settle it on the battlefield, the bed will do just fine. With that, she wins everytime. She knows what sort of things her father would tell her. That's she's a foolish girl, or he would implore her seize the opportunity and keep a hero wrapped tight around her finger - as if your annoying stubborness would ever allow that to happen. What you and Rose have is just a fleeting passion; a fling. Rose would love to cut you down a peg or two with her swordsmanship - or perhaps, she just yearns to conquer your battles in other ways.
"Before you talk of my ego, how about you recall where I had you two nights ago?" Rose scowls at you sharply, using her legs to hook them around your body and twist you both until you were the one on your back, the rain soaking the two of you completely. You reach for your weapon, and Rose's foot shoots out, digging awkwardly into your wrist to prevent you from moving any further. The tip of her sword rests under your chin, a whisper against your skin. She offers a coy smile. "Should I repeat the sweet nothings I had you saying to your team? I'm not so sure it's my ego you should be worrying about."
She twists her boot, just to be cruel, crushing your wrist to watch the flicker of pain in your expression. She wants to kiss you until you can't breathe - maybe it would shut you up.