All birds have different personalities so it is hard to say what might happen in various situations and there is never any guarantee that introducing a new bird will work out favorably, Umi might be very happy in her own cage and the boys may form a bond between themselves. I have had various situations with a mixed flock. I had a male and female together for 8 years, they were together from a young age in their own cage but spent out of the cage time with other males and females and no problems, no eggs no aggression no mating, although he was very protective of her, that was ideal. He passed away last year but I still have her and she spends her days with two males, they are out all day but she sleeps at night with one male, everybody happy. I acquired another pair a brother and sister about 4 years ago, that was a whole different experience, she turned out to be a chronic egg layer and eventually had a cloacal prolapse which was surgically repaired but she had to be permanently separated from the boys so she was moved to a different part of the house and I got another female to be company for her. Sometimes you just cannot predict what will happen but with multiple birds and mixed genders you have to be prepared for anything. The brother and sister were supposed to be brothers but surprise, one turned out to be a female. as a young bird her cere looked just like a young male, it was dark pink, so we all thought it would eventually turn blue but instead it started turning tan
If you were to get another female to house with Umi it may or may not work out and you might end up with 3 cages if it didn't. What is her personality like, is she bossy?
