Hello there and welcome to BYC!
What a pretty bird!
Definitely add this bird slowly to your existing flock. Put her in a cage within the coop and run for 3 to 4 weeks. Everybody sees, nobody touches. Then in 3 or 4 weeks you can put her in the flock. Watch that she is not too harassed and definitely intervene if it turns bloody. Put out extra feeding and watering stations as the existing flock can starve her out of food and water until she works into the flock which can take months.
Good luck and welcome to our flock!

What a pretty bird!
Definitely add this bird slowly to your existing flock. Put her in a cage within the coop and run for 3 to 4 weeks. Everybody sees, nobody touches. Then in 3 or 4 weeks you can put her in the flock. Watch that she is not too harassed and definitely intervene if it turns bloody. Put out extra feeding and watering stations as the existing flock can starve her out of food and water until she works into the flock which can take months.
Good luck and welcome to our flock!