If you're willing to time travel, I usually time travel 3 days and keep going until someone pings along with the villager I want out. If you're lucky and she pings, time travel to her moving date, the date she says.
Pray Keep talking to them be thier best friend, it's always the ones you try the most to keep who want to leave the most. I have also found that almost all of my villagers try to leave the day after their birthday, weather you give them a gift or not. I've been trying to get Bam out for awhile but he's a stubborn one. I wish there was a solid way to make them leave quickly but the developers just didn't give it to us. Good Luck