She had done it long before they ever started sharing a bed.
His shower was the only one on the boat, so she'd slowly (and very carefully) started to leave a few of her own things in the cramped space. She was so careful about keeping her things together, as if she were afraid he would see her things as an intrusion and she wanted to keep her invasion into his space as minimal as possible. He'd tried to tell her that the shower was a common space, and that she wasn't intruding, but it would be another week before she actually seemed to take him up on the offer.
And even then it was as small as simply leaving her toothbrush on the edge of the sink.
Eventually, and thankfully, she became even more comfortable on the Rouge and around him. They fell into a routine of sorts—she was a bit of an early riser, compared to him so part of their routine became that when she was ready to shower, she'd knock on his door, he'd grab a pillow and a blanket, and he'd move to couch in the stateroom to sleep a bit longer. When she was done, she'd pad out of his room, all smiles and clean smelling, and whisper a "thank you" to him that he'd only mumble back at in his sleep.
A few minutes would pass and then Duke would eventually give up on trying to sleep, and shower himself. Once finished, he stood in his bathroom, rubbing a towel on his head to try to dry his hair. When he looked at the mirror, he noticed that there was something written on his mirror. Not in ink, of course, but in the fog that his shower caused to show up on the mirror itself. She'd written him a message with her fingers on his mirror, just a simple, "Have a good day! Be safe!" with a stupidly cute heart next to a "J".
He couldn't stop the grin that spread across his face at the message.
Not a bad way to start the day if he was being honest.