I had Coco for at over a year before I finally let her go. She had pinged me a bunch of times and I felt guilty :c She was the last of my original villagers and I loved her. I was initially creeped out when I first got the game, what with her big empty eyes and such, but I grew to adore her.
Now it's probably Lolly that I've had for the longest, I'd say for also about a year. Love her just as much!