Don't be sad. You two have been nudged into opening your hearts to another kitty- one way or another. Chances are good- with a proper introducion- that Nakita will take up with another kitty. My RB Tex was 4ish when we adopted Georgia. They were the bestest of friends, and no one touched that relationship- not any of the next 6 that came after Georgie.

Good luck finding the little kitty for you- outside your window, or at the shelter.