I hate to make one of these posts, but holy moly she looks like...
..model Jessica Serfaty. I haven't started watching Riverdale yet, but I happened to come across a few scenes on youtube and I immediately came here to see if it was her. It's unreal how similar they look.
Jessica:
https://antm411.files.wordpress.com/2010/03/jessica070.jpg
Lili:
http://www.imdb.com/name/nm3929887/mediaviewer/rm3965198080
They obviously aren't identicle, but they definitely could pass as sisters..