I heard that if you go to your abandoned missions and redo the quest for HoW it should give it to you. The quest is called A Kell Rising I'm pretty sure.

A lot of people say you have to be rank 3. But let me shine some light on this. Lots of people have gotten and have been as low as rank 0 with her. This quest seems to be bugged. Try to level her up at least once. It doesn't seem to matter what lvl you move to or from but a lot of people were only rank 2 before they didn't get the weapon so the moved to rank 3 and it became the rank you needed to be. But it's been proven that you can get it with a lower rank and not get it even when you're a much higher rank. I'm rank 4 with my titan and I didn't get it. Though people have been reporting they've completed the wolves quest line that you can go pick up from the abandoned quest kiosk. And once they completed the last quest then bam, there it was. Who knows what's wrong with it, but it's obviously bugged.

You have to be rank 3 with her.