You wait until you convince her to leave, and when she has her stuff packed in boxes, in her house, then someone can come and get her, or she'll just disappear. I believe this is how it works...
TT day by day, talking to villagers until you either hear a rumor or she pings. If she pings, and you answer it, and she changes her mind, reset, and ignore. If you hear a rumor, ignore her entirely.