Well Beccy, I did the exact opposite, I got my sun conure first then my grey. My sun is jealous of the grey but she is on my shoulder more than the grey is, and they do not get along, but they tolerate each other. As long as I keep one on each shoulder they are fine, but I cannot let one of them creep over onto the opposite side or the grey gets nipped. I think if you handle it right, each will be ok with the addition of another bird.
I can tell you really liked this conure and I am sure she will come to accept you and bond with you in time, and Brian will be ok with it as long as you don't let the amount of time you spend with him suffer from the addition of the conure. You can do it, I know you can, and you will be happy with both of them, I'm sure. Give the little bird a chance, she will be so loving, you will wonder why you hadn't already owned one before.