Well they do have an out with comic version of Black Canary who does come from Earth 2 to Earth 1 to be BC. Maybe that's what they are laying the groundwork for in that future Flash episode...
lol who knows this is a show where sara and thea were dead and both raised from the dead
a show where oliver hsa prob taken like 50 arrows to various body parts and never bled out or rarely needed medical attention, a show where oliver was sliced up and kicked 50 feet and still survived. A show where you can be in a vehicle that takes 100 shots and you get out unscathed
A show where you can be paralyzed and get some nano tech and be perfect again
a show where there are some tricks to fake your death like oliver made that women do in the flashback
a show where bees can be inside you expanding but you'll poop it out and be ok
a show where you can get your hand cut off and not be rahs al gul one week but the next week have some trained assasins who get disposed off easily and yet you still hold your own with one hand
a show where dudes can take a arrow like they did this episode and be ok but 15 min later a chick takes a arrow and croaks
and a show that the writers have no balls and if people complain they will just have flash show up and run back in time, or bring over laurels doppleganger from earth two and carry on