Dashiel travels a lot, on purpose. He hasn't stayed in one place for too long, other than training on Babylon. So he could conceivably been anywhere for a while and met her. I see you have an apartment in Gasworks that needs filling, he could potentially take that, especially if Issy would be willing to help provide his alias with alibis and such! Just the sort of "Yeah I know that dude, that's totally Eric from 2B" kind of thing.