Cupid’s cell was seen alongside villains like Cheetah and Grodd, and Barry openly stated it must’ve been where Amanda Waller imprisoned the team.
Cupid’s last Arrow-verse appearance actually happened on The Flash, in which is was revealed she had found her way back into A.R.G.U.S. following her recapture.
It hasn’t been long since Arrow fans have seen Ricardo Diaz or Joe Wilson, but China White and Cupid haven’t been seen on the show since Season 5 in “The Sin-Eater.”