You have to island hop with the nook mile tickets There's a (small) chance she will be there and you can invite her back. So bring a lot of tickets Or if you can get the amiibo card you can invite her to your campsite and she will ask to live on your island again.
Edit: Or when you have an empty plot and someone has Plucky in boxes you can invite her from there.
1)Find her on a mystery island and invite her to move in
2)Adopt her from someone else's town (she must be moving out)
3)If she shows up in your campsite, you can invite her from there
4)Use amiibo