First off, where are you from so we can tell if its breeding season?
Second, yes please remove the spare female, as an aggressive breeding female can kill other birds.
What size is the cage they are in? Do they have a nesting box? Is there space for a nesting box?
What do you feed them?

all these questions will help us to give you the best and most accurate advice we can!
Thanks and good luck, let us know!