Hey! I love the character, so we should totally do something? Maybe she is the ex that remains on good terms with him? Like they made the terrible idea to try and start dating, but were both still dealing with their respective guilt and memories so things fell apart pretty quickly?
But after a period of time, they remained friends and hang out regularly? I could totally see him not using his voice around her, instead choosing to write things because it 'evens the field'. And that probably results in him leaving little doodles around for her to find in her quarters or where she likes to plant her flag.