Of course, beyond the fact that Black Siren and Canary may fight each other in this sequence, there’s another possibility that we feel compelled to consider: they may actually be secretly working together.
After all, Team Arrow has utilized deep cover tactics like this before; it’s not outside the realm of possibility to imagine that Oliver secretly recruited Siren at some point.
With the henchmen unconscious on the ground (thus leaving no witnesses to their interaction) the smiles on the faces of these ass-kicking women could also indicate a hidden trust.
Even though she served as an antagonist in Arrow last season, there have been subtle hints at a possible redemptive arc for Black Siren ever since she first appeared in the Arrow-verse during an episode of The Flash.