This is actually pretty easy to get. Treat it like the D1 Thorn quest... Each day pick up and complete every bounty you can from Ada, but DO NOT turn them in. Pick up other bounties and do the same, complete but do not turn in. Fill up your entire Bounty Board with finished bounties and WAIT a day. After you've waited, slowly start turning the bounties in one by one (recommend 1 every couple of seconds), and leave the Ada bounties towards the end. For me, after doing this once, I was able to get a rare bounty from Ada. Hope this helps you!!!