Once Upon a Time / Rizzoli & Isles
In my head!canon, Jane and Emma knew each other from Boston. Jane got her the bounty hunter job and worked a few cases with her, then they moved in together as flatmates because Emma needed a place to stay and then, well, things got complicated. They got together for a while but Emma screwed it up by keeping secrets from Jane, job-related and personal.
Jane could not put up with Emma never learning to trust her fully and so she left. This takes place approximately two months before Emma left for Storybrooke.