So I have a few potential ideas here, the primary one being fellow YouTuber and collaborator. Mimi isn't really a model herself, but she's really into things like fashion and music, so I could see her being a fan of FAV, and of Nico.

The other thing I was thinking is, if you're looking for family for Nico, having the two of them being related. Mimi is half-Japanese and did a decent amount of traveling between Recolle and AU-Tokyo, so if they're related they would know each other decently well. It might also help Nico get settled by having family in Recolle.