Don't think Rimil is a lock for Rio by any means...unless the federation simply decides that whoever won the quota will be the ones going, like they did in 2012 (the quota was won last year by Deepika, Rimil and Laxmirani)
In the Colombia world cup, 4 archers competed for India - Deepika, Bombayala, Laxmirani Majhi and Rimil. Rimil had the lowest qualification score out of the 4 and thus the other 3 competed in the team event and won Silver. So Rimil was not part of that silver-winning team...I think eventually it will be 3 of these 4 going to Rio but either Rimil or Bombayala can miss out (Deepika is obviously a lock and Majhi has been doing very well in the past year).